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K Xu

Publications and source records attributed to K Xu.

At least 163 records · Page 9Linked to original sources
PubMed1998

[Study on expression of Evi1 and MDS1-Evi1 genes in myelodysplastic syndromes].

OBJECTIVE: To investigate expression of Evi1 and MDS1-Evi1 genes in myelodysplastic syndromes (MDS) and its role in pathogenesis of MDS. METHODS: Expression of Evi1 and MDS1-Evi1 genes was examined in 31 MDS, 11 post MDS acute myeloid leukemia (post MDS AML) and 34 de novo AML patients by a semi-quantitative RT-PCR. RESULTS: Evi1 expression was not detected in 8 normal controls, but low MDS1-Evi1 expression levels (MDS1-Evi1/GAPDH < 0.1) detected in 3 of the 8 controls. Evi1 mRNA was expressed in 1 of 8 RA, 8 of 13 RAEB and 6 of 9 RAEB-t patients, and the percentage of Evi1 expression in RAEB(t) patients was higher than that in RA(P < 0.05). MDS1-Evi1 expression was detected in 5 of 8 RA, 9 of 13 RAEB and 5 of 9 RAEB-t patients, and MDS1-Evi1 expression levels (MDS1-Evi1/GAPDH > 0.1) in the patients were markedly higher than those in the controls. Evi1 expression was gradually increased in 4 of 5 RAEB-t patients with transformation from MDS to AML. The percentages of Evi-1 and MDS1-Evi1 expression in post MDS AML patients were higher than those in de novo AML (P < 0.01 and P < 0.05, respectively). The numbers of colony formation of progenitor cells in Evi1 and MDS1-Evi1-positive MDS patients were decreased as compared with Evi1 and MDS1-Evi1-negative patients. CONCLUSION: Abnormal expression of Evi1 and overexpression of MDS1-Evi1 might play a certain role in the pathogenesis or progression of MDS and post MDS AML.

Adult↗
PubMed1998

Transmission and natural regulation of infection with Ascaris lumbricoides in a rural community in China.

A longitudinal study on a cohort of 215 people who remained untreated from June 1993 to June 1994 was carried out using fecal egg counts to examine the course of transmission and aspects of the natural regulation of the infection with Ascaris lumbricoides. The results indicate that the parasite population remained relatively stable during the years since overall prevalence remained steady above 60%. About 40% of the people in the cohort retained their infection intensity status throughout the year, in terms of light, medium, and heavy infections. The regulation of infection in the population could be attributed to the tendency for the loss of worms from people with initial light infections and the movement to medium infection intensity status of people with both light and heavy infections. Compared with adults, children showed a stronger tendency of retaining initial medium infections but weaker tendencies for keeping initial light infections and clearing themselves of infection. Predisposition to light and medium infections was detected in people who had experienced an uninfected period of 4-12 mo before reinfection was established.

Adolescent↗
PubMed1997

Molecular cloning of the gene for mouse leukotriene-C4 synthase.

Leukotriene C4 (LTC4) synthase (LTC4S), an integral membrane protein, catalyzes the conjugation of leukotriene A4 with reduced glutathione to form LTC4, the biosynthetic parent of the additional cysteinyl leukotriene metabolites. An XmnI-digested fragment of a P1 clone from a 129 mouse ES library contained the full-length gene of 2.01 kb for mouse LTC4S. The mouse LTC4S gene is comprised of 5 exons of 122, 100, 71, 82 and 241 nucleotides, with intron sizes that range from 76 nucleotides to 937 nucleotides. The intron/exon boundaries are identical to those of the human genes for LTC4S and 5-lipoxygenase-activating protein (FLAP). Primer extension demonstrated a single transcription-initiation site 64 bp 5' of the ATG translation-start site. Nucleotide sequencing of 1.2 kb of the 5' flanking region revealed multiple putative sites for activating protein-2, CCAAT/enhancer-binding protein, and polyoma virus enhancer-3. Fluorescent in situ hybridization mapped the mouse LTC4S gene to mouse chromosome 11, in a region containing the genes for interleukin 13 and granulocyte/macrophage-colony-stimulating factor, and orthologous to the chromosomal location of 5q35 for the human LTC4S gene. Thus, the mouse LTC4S gene is similar in size, intron/exon organization and chromosomal localization to the human LTC4S gene. Recent mutagenic analysis of the conjugation function of human LTC4S has identified R51 and Y93 as critical for acid and base catalysis of LTA4 and reduced glutathione, respectively. A comparison across species for proteins that possess LTC4S activity reveals conservation of both of these residues, whereas R51 is absent in the FLAP molecules. Thus, within the glutathione S-transferase superfamily of genes, alignment of specific residues allows the separation of LTC4S family members from their most structurally similar counterparts, the FLAP molecules.

Amino Acid Sequence↗
PubMed1997

Site-directed mutagenesis of human leukotriene C4 synthase.

The functional characteristics of leukotriene C4 synthase (LTC4S), which specifically conjugates leukotriene A4 with GSH, were assessed by mutagenic analysis. Human LTC4S and the 5-lipoxygenase-activating protein share substantial amino acid identity and predicted secondary structure. The mutation of Arg-51 of LTC4S to Thr or Ile abolishes the enzyme function, whereas the mutation of Arg-51 to His or Lys provides a fully active recombinant protein. The mutations Y59F, Y97F, Y93F, N55A, V49F, and A52S increase the Km of the recombinant microsomal enzyme for GSH. The mutation Y93F also markedly reduces enzyme function and increases the optimum for pH-dependent activity. The deletion of the third hydrophobic domain with the carboxyl terminus abolishes the enzyme activity, and function is restored by the substitution of the third hydrophobic domain and carboxyl terminus of 5-lipoxygenase-activating protein for that of LTC4S. Mutations of C56S and C82V alone or together and the deletion of Lys-2 and Asp-3 of LTC4S do not alter enzyme function. The direct linkage of two LTC4S monomers by a 12-amino acid bridge provides an active dimer, and the same bridging of inactive R51I with a wild-type monomer creates an active pseudo-dimer with function similar to that of the wild-type enzyme. These results suggest that in the catalytic function of LTC4S, Arg-51 probably opens the epoxide ring and Tyr-93 provides the thiolate anion of GSH. Furthermore, the monomer has independent conjugation activity, and dimerization of LTC4S maintains the proper protein structure.

5-Lipoxygenase-Activating Proteins↗
PubMed1997

Babesiasis in Nanjing area, China.

This article discusses the tick-borne babesiases which harm dairy cattle, buffaloes and dogs. In addition, the pathogen, vector, seasonal occurrence, hosts, symptoms, pathological changes and treatment are summarized and analysed. The pathogens in this area were identified as Babesia bigemina, B. bovis and B. gibsoni; the vectors as Boophilus microplus, Rhipicephalus haemaphysaloides, Haemaphysalis longicornis. Affected buffaloes were found from April to September, peak numbers occurred between May and July. Affected dairy cattle were most numerous in July and August. Hunting dogs were the most affected dogs. Infected dogs were found from February until the beginning of December; peak numbers occurred from September to November. Affected animals were acute cases. Symptoms and pathological changes were obvious, but jaundice was rare in dogs. Acaprin, acriflavine, imidocarb and berenil were used early and late. Their effect was ideal but resistance has developed to these drugs.

Acriflavine↗
PubMed1997

The outer surface protein A (OspA) vaccine against Lyme disease: efficacy in the rhesus monkey.

The efficacy of an outer surface protein A (OspA) vaccine in three different formulations was investigated in the rhesus monkey. The challenge infection was administered using Ixodes scapularis ticks that were infected with the B31 strain of Borrelia burgdorferi. Protection was assessed against both infection and disease, by a variety of procedures. Some of the animals were radically immune suppressed, as an attempt to reveal any putative low level infection in the vaccinated animals. The significant difference found between the spirochaetal infection rates of ticks that had fed on vaccinated vs. control monkeys, lack of seroconversion in the vaccinated animals, and the absence of spirochaetal DNA in the skin of vaccinated animals in the weeks following the challenge, indicate that vaccinated monkeys were protected against tick challenge. The post-mortem immunohistochemical and polymerase chain reaction analyses, however, suggest that these monkeys may have undergone a low-level infection that was transient.

Animals↗
PubMed1997

Association analysis of the dopamine D4 gene exon III VNTR and heroin abuse in Chinese subjects.

Although social and cultural influences are clearly important, family, twin and adoption studies indicate that genes contribute significantly to substance abuse. Substance abuse is associated with novelty seeking, a heritable human personality trait which may be influenced by alleles of the dopamine D4 (DRD4) gene exon III VNTR. Consequently Kotler et al analysed the DRD4 VNTR in opiate-dependent subjects from Israel, and found a significant excess of the 7-repeat allele. We have attempted to replicate this finding using a Han Chinese case-control sample of 121 heroin-dependent subjects and 154 normal controls. We found two 7-repeat alleles which occurred exclusively in the patient group, and overall there was an excess of longer alleles, which did not reach significance (chi 2 = 7.04; P = 0.07). When the D4 VNTR was divided into 'long' (5-7 repeats) and 'short' (2-4 repeats), a significant excess of long alleles was observed in the patient group (P = 0.023, one-tailed), with an odds ratio of 2.30 (95% CI 1.07-4.93). We conclude that our findings support the hypothesis that alleles of the DRD4 exon III VNTR are susceptibility factors for heroin abuse.

Adolescent↗
PubMed1997

Catechol-O-methyltransferase Val158Met polymorphism: frequency analysis in Han Chinese subjects and allelic association of the low activity allele with bipolar affective disorder.

Catechol-O-methyltransferase catalyses the O-methylation of biologically active or toxic catechols and is a major component of the metabolism of drugs and neurotransmitters such as L-dopa, noradrenaline, adrenaline, and dopamine. Human catechol-O-methyltransferase activity is an autosomal partially dominant trait and is strongly associated with a valine to methionine substitution at codon 158 of the protein. About 25% of Caucasians have low activity, 50% intermediate activity and 25% high activity as determined by either phenotypic or genotypic measurement. In black populations, the low activity allele (Met158; COMTL) is less frequent with about 7% being homozygous. Using a PCR based genotyping assay, we report that the Met158 allele is also less frequent in normal Han Chinese subjects with about 3% of the population being homozygous. Because of its role in catecholamine metabolism and several lines of evidence pointing to a locus for psychosis near the COMT gene on chromosome 22q11, we have analysed the COMT Val158Met polymorphism as a candidate susceptibility factor for bipolar affective disorder. We report an association between bipolar affective disorder and the Met158 allele (p = 0.004) and genotype (p = 0.01) in 93 affected Chinese subjects and 98 controls. We hypothesize that either the low activity allele of catechol-O-methyltransferase is a risk factor for bipolar affective disorder in Chinese populations or is in linkage disequilibrium with a nearby susceptibility gene or polymorphism.

Bipolar Disorder↗
PubMed1997

Alterations of cardiac alpha 1-adrenoceptor subtypes in hypothyroid rats.

1. Alterations in the cardiac alpha 1-adrenoceptor and its subtypes in hypothyroid rats were studied by radioligand binding assays and reverse transcription-polymerase chain reaction (RT-PCR). Hypothyroidism was created by feeding rats with 0.2% 2-thiouracil solution instead of daily drinking water for 20 days. 2. The density of cardiac alpha 1-adrenoceptors (Bmax) was increased from 67.5 +/- 4.3 fmol/mg in control rats to 81.1 +/- 7.2 fmol/mg (P < 0.05) in hypothyroid rats. 3. Compared with control rats, in hypothyroid rats the percentages of high-affinity sites for (+)-niguldipine and 5-methylurapidil were increased from 13.8 +/- 5.6 and 31.9 +/- 6.3%, respectively, to 24.9 +/- 7.3 and 45.5 +/- 2.4%, respectively (both P < 0.05), while those for BMY7378 were decreased from 37.2 +/- 8.9 to 23.8 +/- 8.4% (P < 0.05), respectively. The percentage of high-affinity sites for WB4101 was not significantly different in control and hypothyroid rats (43.3 +/- 9.1 and 39.4 +/- 3.6%, respectively). 4. Reverse transcription-PCR experiments revealed that the steady state levels of mRNA for alpha 1A- and alpha 1B-adrenoceptors were increased, while those for alpha 1D-adrenoceptor were decreased in the hearts of hypothyroid rats. 5. The concentration-contraction response curves for noradrenaline in the presence of a beta-adrenoceptor antagonist in control and hypothyroid rats showed that the maximal response was reduced from 344 +/- 58 to 200 +/- 23 mg, respectively (P < 0.05). 6. The data suggest that in hypothyroid rats the total number of cardiac alpha 1-adrenoceptors is increased. The change is subtype-selective, with levels of alpha 1A- and alpha 1B-adrenoceptors being increased and levels of alpha 1D-adrenoceptors being reduced. Furthermore, the positive inotropic response mediated by alpha 1-adrenoceptors is reduced in hypothyroid rats.

Adrenergic alpha-Antagonists↗
PubMed1997

Rifampicin carrying polyhydroxybutyrate microspheres as a potential chemoembolization agent.

In this study, we attempted to prepare microspheres from a microbial biodegradable polyester, i.e. polyhydroxybutyrate (PHB) as a potential chemoembolization agent. The drug loaded PHB microspheres were prepared by a solvent evaporation technique, in which methylene chloride, distilled water, and polyvinyl alcohol were utilized as the solvent, dispersion medium, and emulsifier, respectively. Microspheres were obtained within a size range of 5-100 microns by changing the initial polymer/solvent ratio, emulsifier concentration, stirring rate, and initial drug concentration. It was possible to obtain PHB with very narrow size distributions by applying gravity field-flow fractionation technique. Very high drug loadings of up to 407.6 mg rifampicin/g PHB were achieved. Drug release rates were very rapid. Almost 90% of the drug loaded was released in about 24 h. Both the size and drug content of PHB microspheres were found to be effective in controlling the drug release from these microspheres.

Antibiotics, Antitubercular↗
PubMed1997

[Biopsy of labial salivary glands and lacrimal glands in the diagnosis of Sjögren's syndrome].

OBJECTIVES: To determine the diagnostic value for Sjögren's syndrome (SS) by evaluating the presence of focal adenitis in labial salivary gland (LSG) and lacrimal gland (LG) biopsy specimens. METHODS: 109 suspected cases with SS underwent the biopsies. The diagnostic criteria of Fox et al. were followed. Both Chisholm-Manson's grading standard and Greenspan's focus score were used for the evaluation. RESULTS: Myoepithelial islands and severe lymphocyte infiltration with germinal centers were observed only in LG biopsy specimens. The lymphocytic foci scored of LG were significantly higher than that of LSG in 23 cases having both biopsy results. The evaluation of both kinds of specimen for such a patient was significantly more effective in diagnosing SS than using either one of them alone. CONCLUSION: We recommend that both LSG and LG biopsies be performed in patients suspected of having SS to reduce false negative results and improve diagnostic accuracy.

Adult↗
PubMed1997

[Loss of heterozygosity on chromosome 17p13.3 in ovarian cancer and cervical cancer].

OBJECTIVE: To identify the loss of heterozygosity (LOH) on chromosome 17p13.3 in ovarian cancer and cervical cancer. METHODS: The frequency of LOH on chromosome 17p13.3 in DNA samples from 24 ovarian cancers, 9 cervical cancers, and 13 non-malignant gynecological diseases were determined respectively, using Southern blot method with probe PYNZ. 22. RESULTS: LOH on 17p13.3 was found in 12 of 24 (50.0%) ovarian cancers (including a borderline mucinous cystadenoma), 4 of 9 (44.4%) cervical carcinomas, and 1 of 13 (7.7%) non-malignant gynecological diseases, which was cervical intraepithelial neoplasm III (CIN III) (P < 0.01). CONCLUSION: These results show that LOH on 17p13.3 is associated with ovarian cancer and cervical cancer, suggesting that detection of LOH on 17p13.3 may be helpful to understand the molecular pathogenesis of ovarian cancer and cervical cancer.

Adult↗
PubMed1997

[Study on prethrombotic state in patients with paroxysmal nocturnal hemoglobinuria].

OBJECTIVE: To explore the mechanism of thrombogenesis in patients with paroxysmal nocturnal hemoglobinuria (PNH). METHODS: Thirteen parameters concerning endotheliocytes, platelets, blood coagulation, and fibrinolysis were measured in 21 PNH patients. RESULTS: As compared with normal controls, plasma fibrin peptide A (FPA) levels were significantly higher, but antithrombin-III (AT-III) and protein C (PC) antigen levels lower in the PNH patients. Plasma tissue plasminogen activator (t-PA) activities were significantly lower while plasminogen activator inhibitor (PAI) activities markedly higher in the patients than those in the controls. The levels of the blood coagulation and fibrinolysis parameters changed more notably during the occurrence of thrombosis and hemoglobinuria episodes in the PNH patients. Platelet adhesion rates, platelet aggregation rates, beta-thromboglobulin (beta-TG), and granule membrane protein-140 (GMP-140) were within the normal ranges. Plasma vWF:Ag and endothelin-1 (ET-1) concentrations were normal in the patients as well. CONCLUSION: Prethrombotic state is present in PNH patients, which may be caused by hypercoagulability and low fibrinolytic activity.

Adult↗
PubMed1997

[Study on transposition behavior of IS5376 in Bacillus stearothermophilus].

IS5376 and IS5377 are two transposable elements discovered in Bacillus stearothermophilus. Analysis of random samples revealed that the frequency of transposition of IS5376 from CU21 chromosome to plasmids pFDC5 and pFDC12 was much higher at 65 degrees C than that at 48 degrees C while that of IS5377 was very low at both 48 degrees C and 65 degrees C. The exact nature of the temperature effect is obscure at present from evidences obtained so far it is concluded that this is a consequence of the innate property of IS5376. Furthermore, it was found that a certain degree of site specificity in transposition was evident and that a direct repeat of 4 or 5 bp of the target DNA appeared at the site of transposition.

Base Sequence↗
PubMed1997

[A study on polycyclic aromatic hydrocarbon-DNA adduct in lung cancer patients exposed to indoor coal-burning smoke].

The objective of this study is to explore the etiology and early risk evaluation of lung cancer in Xuanwei County, Yunnan Province of China. Polycyclic aromatic hydrocarbon (PAH)-DNA adduct in brushing cells from fibrobronchoscopy was determined in 30 cases with lung cancer in Xuanwei County and 10 controls in Kunming, Yunnan Province by 32P-postlabelling assay. Results showed that PAH-DNA levels in lung cancer patients of Xuanwei County were much more higher than those in controls. It suggested that air pollution caused by indoor coal-burning associated directly with the occurrence of lung cancer, and detection of DNA adduct could be used as an indicator for its risk assessment in population.

Air Pollution, Indoor↗
PubMed1996

Expression of the retinoblastoma (RB) tumor suppressor gene inhibits tumor cell invasion in vitro.

To determine if replacement of the retinoblastoma (RB) tumor suppressor gene could inhibit invasion of RB-defective tumor cells, the capacity of tumor cells to migrate or invade was quantitated by the Boyden chamber assay. The studies were done in a diverse group of stable RB-reconstituted human tumor cell lines, including those derived from the osteosarcoma and carcinomas of the lung, breast and bladder. The expression of the exogenous wild-type RB protein in these tumor cell lines was driven by either a constitutively active promoter or an inducible promoter. It was found that significantly more tumor cells from the parental RB-defective cell lines and the RB revertants than from the RB-reconstituted RB+ cell lines penetrated through the Matrigel (P<0.001, two-tailed t-test), although both RB+ and RB- cells migrated at approximately the same rate on uncoated polycarbonate filters in the Boyden chambers. Of note, the inhibition of invasiveness of various RB-defective tumor cells by RB replacement was apparently well correlated with suppression of their tumorigenicity in vivo. In contrast, although either functional RB or p53 re-expression effectively suppressed tumor formation in nude mice of the RB-/p53null osteosarcoma cell line, Saos-2, replacement of the wild-type p53 gene had much less impact on their invasiveness as compared to the RB gene. These studies provided an insight into the broader biological basis of the RB-mediated tumor suppression in RB-defective tumor cells.

Animals↗
PubMed1996

Molecular cloning, expression and characterization of mouse leukotriene C4 synthase.

Leukotriene C4 synthase (EC 2.5.1.37) catalyzes the conjugation of reduced glutathione (GSH) with leukotriene A4 to form the intracellular parent of the proinflammatory cysteinyl leukotrienes. Human leukotriene C4 synthase shares substantial amino acid identity in its consensus N-terminal two-thirds with 5-lipoxygenase-activating protein and has a region (residues 37-58) that exhibits 46% amino acid identity with a domain of this protein (residues 41 -62) to which an inhibitor binds. We have now cloned mouse leukotriene C4 synthase CDNA using the polymerase chain reaction to screen a mouse pcDNA3 expression library with oligonucleotide primers based on the translated human leukotriene C4 synthase cDNA sequence. Mouse leukotriene C4 synthase cDNA is 667 bp in length, including the poly(A)-rich tail, and shows 87% similarity with the human cDNA within the open reading frame. The deduced 150-amino-acid sequence of mouse leukotriene C4 synthase (differs from the human enzyme by only 18 amino acids, of which 9 reside at the C terminus. The potential N-glycosylation site, two protein kinase C phosphorylation sites, the two cysteine residues, and the putative inhibitor-binding domain (substitutions Thr4l-->Ser and Tyr50-->Phe) were conserved in mouse leukotriene C4 synthase. Northern blot analysis indicated that the leukotriene C4 synthase RNA transcript is widely distributed. The Km values for leukotriene A4 methyl ester, leukotriene A4 free acid and GSH were 7.6 microM, 3.6 microM and 1.6 mM, respectively, for purified human recombinant enzyme, and 10.3 microM, 2.5 microM and 1.9 microM, respectively, for purified recombinant mouse enzyme; the corresponding Vmax values were 2.5, 1.3 and 2.7 micromol x min(-1) x mg(-1) protein, respectively, for human enzyme, and 2.3, 1.2 and 2.2 micromol x min(-1) x mg(-1) protein, respectively, for mouse enzyme. The 5-lipoxygenase-activating-protein inhibitor, MK-886, was active against both human and mouse recombinant leukotriene C4 synthase with IC50 values of 3.1 microM and 2.7 microM respectively. These findings confirm that the leukotriene C4 synthases belong to a gene family that includes the 5-lypoxygenase-activating protein and suggest that the C-terminal domain of leukotriene C4 synthase may not be critical for its conjugation function.

Amino Acid Sequence↗