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A Xu

Publications and source records attributed to A Xu.

108 records · Page 6Linked to original sources
PubMed1994

17 beta-estradiol preserves endothelial vasodilator function and limits low-density lipoprotein oxidation in hypercholesterolemic swine.

BACKGROUND: Cardiovascular events are less prevalent in premenopausal women and women receiving estrogen replacement than in postmenopausal women or men. Endothelium-derived relaxing factor (EDRF) is an important local modulator of vascular tone, and abnormal endothelial function is related, in part, to the oxidative modification of low-density lipoprotein (LDL). Estrogens possess substantial antioxidant activity and inhibit LDL modification in vitro. METHODS AND RESULTS: We investigated the effects of 17 beta-estradiol (E2) on endothelial vasomotor function in cholesterol-fed miniature swine. Animals underwent ovariectomy or a sham procedure and received E2 or placebo via implant yielding three groups: sham, ovariectomy (E2 placebo), and implant (E2 implant). After 16 weeks, coronary arteries were harvested and endothelial function was examined in vitro. Vessels from the sham and implant groups demonstrated preserved endothelium-dependent relaxation to bradykinin, substance P, and A23187. Vessels from the ovariectomy group exhibited impaired relaxation to bradykinin and substance P (P < .05 versus sham and implant groups) but not to A23187. Plasma E2 levels were strongly correlated with the response to bradykinin (R = .82, P < .001), substance P (R = .64, P < .01), and A23187 (R = .65, P < .01). Compared with the ovariectomy group, LDL derived from the sham and implant groups was markedly resistant to ex vivo oxidation (P < .05), and this effect correlated with preserved endothelium-dependent relaxation to bradykinin (R = .62, P < .03) and substance P (R = .61, P < .03). CONCLUSIONS: Thus, E2 preserves endothelial function in cholesterol-fed swine in association with protection of LDL against oxidative modification. These data suggest that E2 may, in part, favorably affect vascular function and coronary artery disease by virtue of its antioxidant properties.

Animals↗
PubMed1994

Low-dose alpha-tocopherol improves and high-dose alpha-tocopherol worsens endothelial vasodilator function in cholesterol-fed rabbits.

Abnormalities in endothelium-dependent arterial relaxation develop early in atherosclerosis and may, in part, result from the effects of modified low-density lipoprotein (LDL) on agonist-mediated endothelium-derived relaxing factor (EDRF) release and EDRF degradation. alpha-Tocopherol (AT) is the main lipid-soluble antioxidant in human plasma and lipoproteins, therefore, we investigated the effects of AT on endothelium-dependent arterial relaxation in male New Zealand White rabbits fed diets containing (a) no additive (controls), (b) 1% cholesterol (cholesterol group), or 1% cholesterol with either (c) 1,000 IU/kg chow AT (low-dose AT group) or (d) 10,000 IU/kg chow AT (high-dose AT group). After 28 d, we assayed endothelial function and LDL susceptibility to ex vivo copper-mediated oxidation. Acetylcholine-and A23187-mediated endothelium-dependent relaxations were significantly impaired in the cholesterol group (P < 0.001 vs. control), but preserved in the low-dose AT group (P = NS vs. control). Compared to the control and cholesterol groups, vessels from the high-dose AT group demonstrated profound impairment of arterial relaxation (P < 0.05) and significantly more intimal proliferation than other groups (P < 0.05). In normal vessels, alpha-tocopherol had no effect on endothelial function. LDL derived from both the high- and low-dose AT groups was more resistant to oxidation than LDL from control animals (P < 0.05). These data indicate that modest dietary treatment with AT preserves endothelial vasodilator function in cholesterol-fed rabbits while a higher dose of AT is associated with endothelial dysfunction and enhanced intimal proliferation despite continued LDL resistance to ex vivo copper-mediated oxidation.

Acetylcholine↗
PubMed1994

[Study of vocal function following partial laryngectomy with computer analysis system].

Vocal function of 28 patients following partial laryngectomy was studied with HGF-1 personal computer system. The system consists of spectrogram analysis of correlogram and sonogram. The result showed that different phonetic positions have different vocal functions. Vocal function of the patients who had new vocal cord and patients who received supraglottic hemilaryngectomy is nearly normal. Whereas vocal function of patients with supraglottic construction and speaking shunt is very poor. This system appears to be an objective and quantitative tool for vocal function study.

Aged↗
PubMed1994

[Preliminary investigation on acute flaccid paralysis (AFP) cases in Jinan area].

Eighty AFP cases under 12 years old from 6 hospitals in Jinan were investigated. Among them, there were 17 (21.25%) cases with poliomyelitis (POLIO), 40 (50.00%) cases with Guillian-Barre syndrome (GBS) and 23 (28.75%) cases with other AFP diseases. Most AFP cases occurred from May to October and no significant seasonal difference was found for each kind of AFP cases (P > 0.05), but the average age for POLIO cases (1.55 +/- 1.24) was significantly lower than that for non-POLIO AFP cases (3.76 +/- 2.58) (P < 0.01). The reporting rate from hospitals to each level of epidemic prevention station (EPS) for POLIO, GBS and other AFP cases were 100%, 12.50% and 43.75%, respectively (P < 0.01). Sixty-five AFP cases occurred in 6 prefectures around Jinan city. The average incidence rate (per 100,000) for total AFP, non-POLIO AFP and GBS cases among children under 12 years old were 1.11, 0.89 and 0.53, respectively. The results are helpful to estimate the incidence of AFP cases among children in north provinces of China and also indicate that the POLIO surveillance system in Shandong Province at the present is not sensitive enough, so the AFP cases reporting work of hospitals and the surveillance at each level of EPS should be enhanced.

Child↗
PubMed1994

Poliomyelitis surveillance in Shandong Province, China, 1990-92.

In Shandong Province, China, programmes were initiated in 1991 for mass immunization against poliomyelitis and for the immediate reporting of acute flaccid paralysis (AFP). The incidence of non-poliomyelitis AFP was found to be 0.46-0.61 cases per 100,000 children per annum. It appeared that illness resembling the Guillain-Barré syndrome was underreported. The incidence of such illness peaked among children aged 2-3 years. Although laboratory investigations have improved, in 1992 they were still inadequate in nearly a third of confirmed poliomyelitis cases. As the prevalence of wild poliovirus declines in China, reliable laboratory support needs to be established and adequately sensitive and specific AFP surveillance be developed if poliomyelitis is to be eradicated.

Adolescent↗
PubMed1993

Dietary antioxidants preserve endothelium-dependent vessel relaxation in cholesterol-fed rabbits.

Recent evidence suggests that dietary therapy with lipid-soluble antioxidants may be beneficial for patients with atherosclerotic vascular disease but the potential mechanism(s) for these observations remain obscure. Abnormalities in endothelium-dependent control of vascular tone develop early in the course of atherosclerosis and may result from oxidative modification of low density lipoproteins. We examined the role of dietary antioxidants in preserving normal endothelial cell vasodilator function in cholesterol-fed rabbits with particular attention to possible effects on serum lipoproteins, low density lipoprotein oxidation, and atherogenesis. Male New Zealand White rabbits were fed diets containing no additive (controls), 1% cholesterol (cholesterol group), or 1% cholesterol chow supplemented with either beta-carotene (0.6 g/kg of chow) or alpha-tocopherol (1000 international units/kg of chow) for a 28-day period. After dietary therapy, thoracic aortae were harvested for assay of vascular function and for pathologic examination and tissue antioxidant levels. Compared to controls, acetylcholine- and A23187-mediated endothelium-dependent relaxations were significantly impaired in vessels from the cholesterol group (P < 0.001), whereas vessels from animals treated with beta-carotene or alpha-tocopherol demonstrated normal endothelium-dependent arterial relaxation. Preservation of endothelial function was associated with vascular incorporation of alpha-tocopherol and beta-carotene but was unrelated to plasma lipoprotein levels, smooth muscle cell function, or the extent of atherosclerosis. Increased low density lipoprotein resistance to ex vivo copper-mediated oxidation was observed only in the alpha-tocopherol group. Our results suggest that dietary antioxidants may benefit patients with atherosclerosis by preserving endothelial vasodilator function through a mechanism related to vascular tissue antioxidant content and not reflected by assay of low density lipoprotein resistance to ex vivo oxidation.

Acetylcholine↗
PubMed1993

Polymorphism in BoLA-DRB3 exon 2 correlates with resistance to persistent lymphocytosis caused by bovine leukemia virus.

The relationship between polymorphism of the bovine lymphocyte Ag (BoLA)-DRB3 gene and resistance and susceptibility to persistent lymphocytosis (PL) caused by bovine leukemia virus (BLV) was investigated. Exon 2 of the BoLA-DRB3 gene was cloned from animals with BoLA haplotypes previously found to be associated with resistance and susceptibility to PL. Sequence analysis revealed the presence of the amino acids Glu-Arg (ER) at putative Ag binding residues 70 and 71 only in BoLA haplotypes associated with resistance to PL. This correlation was confirmed in a case control study (n = 26) using an allele-specific polymerase chain reaction for the detection of ER at residues 70-71. These results provide a molecular basis for Ir gene control of resistance and susceptibility to PL and suggest that the cellular immune response is important in preventing the in vivo spread of BLV infection.

Alleles↗
PubMed1993

Effect of pH on stability of sarcoplasmic reticulum calcium pump in rabbit heart.

The sarcoplasmic reticulum (SR) membranes isolated from rabbit heart were preincubated at pH 6.8 or 7.8 and their Ca2+ pump properties were compared at pH 6.8. The ATP-dependent azide insensitive oxalate-stimulated Ca2+ uptake was reduced more rapidly from the membranes preincubated at 37 degrees C at pH 7.8 than from those preincubated at pH 6.8. The Ca(2+)-Mg(2+)-ATPase, and the Ca(2+)-dependent formation of 110 kDa acylphosphate were also inhibited by the preincubation at the higher pH. Including 1 mM DTT in the preincubation medium reduced the inactivation. The preincubation at 37 degrees C in the presence or absence of DTT caused membranes to become more leaky as the loss of Ca2+ uptake was more rapid than that of ATPase or the acylphosphate formation. The loss of these activities was not accompanied by a breakdown of the protein as monitored in Western blots. It is hypothesized that the SR Ca2+ pump inactivation involves a key-SH group and that the lower pH provides a compensatory protective mechanism for the SR during acidosis.

Animals↗
PubMed1993

Phosphorylation and activation of the Ca(2+)-pumping ATPase of cardiac sarcoplasmic reticulum by Ca2+/calmodulin-dependent protein kinase.

It is well known that phosphorylation of the membrane protein phospholamban by cAMP-dependent or Ca2+/calmodulin-dependent protein kinase results in the activation of the Ca(2+)-pumping ATPase of cardiac sarcoplasmic reticulum (SR); such enzyme activation is thought to be due to the disruption of an inhibitory interaction of non-phosphorylated phospholamban with the ATPase. We describe here a novel mechanism for the regulation of the ATPase through direct phosphorylation of this enzyme by a Ca2+/calmodulin-dependent protein kinase (CaM kinase) associated with the SR membrane. It is shown that incubation of cardiac SR in the presence of Ca2+ and calmodulin results in the phosphorylation of the ATPase in addition to the previously recognized substrates of CaM kinase, viz. phospholamban and Ca2+ channel. The phosphorylated amino acid in the ATPase has been identified as serine. Phosphorylation of the membrane-bound ATPase is stimulated by exogenous CaM kinase. Furthermore, ATPase purified from cardiac SR is phosphorylated by exogenous CaM kinase and the phosphorylated enzyme displays 2-fold increase in catalytic activity without any appreciable change in its Ca2+ sensitivity. Thus, direct phosphorylation of the Ca(2+)-pumping ATPase by CaM kinase can stimulate its enzymatic activity and, therefore, Ca2+ transport function.

Animals↗
PubMed1993

Epidemiological study on poliovirus isolates from patients with acute flaccid paralysis in Shandong province in China.

In five years from 1988 to 1992, 51 polioviruses were isolated from patients with acute flaccid paralysis in Shandong province in China. Of the 51 poliovirus isolates, 17 were type 1, 18 type 2 and 16 type 3. Twelve type 1 viruses isolated during the period from 1988 to 1990 were shown to be wild strains by serology and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. These wild strains were classified into three groups by PCR-RFLP. The other type 1 isolates were Sabin-like strains. No wild strain was isolated in 1991 or 1992. All isolates of types 2 and 3 during the five years were Sabin-like strains. These data suggest that wild strains of polioviruses will soon be eradicated in Shandong province.

Acute Disease↗
PubMed1992

[A comparison of the effectiveness of mass immunization campaign of trivalent oral poliovirus vaccine (TOPV) by epidemiological serosurvey. Shandong Collaborating Group for Poliomyelitis Control and Surveillance, Jinan, Shandong].

In order to evaluate the effect of TOPV mass immunization campaign, 902 serum samples from two counties of Shandong province were assayed by micro-neutralization test for the neutralization antibodies against poliovirus. The results showed that among children of 0 to 9 year-old groups, the antibody-positive rates and geometric mean titres (GMTs) with poliovirus type 1 to 3 after mass immunization campaign were significantly higher than those before the campaign, respectively. The author considers that it is necessary for poliomyelitis eradication to carry out TOPV mass immunization campaign on the basis of EPI routine immunization.

Antibodies, Viral↗
PubMed1992

Comparison of Abbott fluorescence polarization immunoassay (FPIA) and Roche radioimmunoassay for the analyses of cannabinoids in urine specimens.

Abbott fluorescence polarization immunoassay (FPIA) and Roche Abuscreen radioimmunoassay (RIA) were compared qualitatively with 142 urine specimens containing 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid. Similar qualitative results were obtained in 132 specimens. When discrepent results were observed, all negative results were within 20% of the 100 ng/mL cut-off. We concluded that FPIA and RIA give comparable results to each other.

Cannabinoids↗
PubMed1991

Gap junction protein homologue from Arabidopsis thaliana: evidence for connexins in plants.

An Arabidopsis thaliana library constructed in the pBluescript expression vector lambda ZAP II (Stratagene) was screened with three affinity-purified antibodies raised against (i) rat liver connexin 32, (ii) a polypeptide from soybean root cells that migrates with a molecular mass of 29 kDa in SDS/polyacrylamide gels and is immunologically related to rat liver connexin, and (iii) a synthetic peptide corresponding to a sequence in rat liver connexin 32. A single clone was obtained whose gene product demonstrated immunological crossreactivity with all three reagents. The cDNA from this clone contained 1171 base pairs and coded for a protein of 280 amino acids with a calculated molecular mass of 32,339 Da (migrates as a 29-kDa polypeptide in SDS/polyacrylamide gels). The sequence homology observed between the 32-kDa polypeptide of Arabidopsis and connexin 32 from rat liver, in conjunction with observed similarities in predicted number and distribution of hydrophobic domains, sites for posttranslational modification, and basic pI, provides strong evidence that the biological range for connexin-type proteins may now be considered to include the plant kingdom.

Amino Acid Sequence↗
PubMed1991

Sequencing and genetic analysis of a bovine DQB cDNA clone.

A BoLA-DQB cDNA clone (BoLA-DQ beta-1) was isolated by screening a bovine lymphoblastoid cDNA library with a HLA-DQB genomic clone. The DNA and predicted protein sequences were compared to class II sequences from cattle and other species. BoLA-DQ beta-1 has 92.0% similarity to the coding regions of two previously sequenced BoLA-DQB genomic clones and 69.6% similarity to a BoLA-DR beta pseudogene. However, the first domain encoded by BoLA-DQ beta-1 has 94 amino acids; one more than the predicted size of the products encoded by two previously sequenced bovine DQB genes (BoDQ beta-Q1 and BoDQ beta-Y1). Comparing all coding regions, BoLA-DQ beta-1 has greater nucleotide similarity to HLA-DQB sequences than to I-A beta, HLA-DRB and I-E beta sequences. Like the HLA-DQB gene product, the cytoplasmic domain of the predicted protein encoded by BoLA-DQ beta-1 is eight amino acids shorter than that of I-A beta, HLA-DRB and I-E beta molecules. Six clone-specific amino acid substitutions were identified in the beta 1 domain of BoLA-DQ beta-1, including an unusual cysteine residue at position 13 which is believed to be positioned on a beta-strand and face into the antigen recognition site. Southern blot analysis of PvuII-digested genomic DNA from a paternal half-sibling family (sire, and six dam-offspring pairs) using BoLA-DQ beta-1 as a probe, revealed five allelic PvuII RFLP patterns, including two patterns not previously described, that cosegregated with serologically-defined BoLA-A (class I) alleles. The evolution, polymorphism and function of a transcriptionally active BoLA-DQB gene can now be readily studied using this DQB cDNA clone as a source of allele and locus-specific oligonucleotide primers.

Amino Acid Sequence↗
PubMedDate not supplied

Outbreaks of paralytic poliomyelitis and polio surveillance in Shandong province of China.

Widespread outbreaks of paralytic poliomyelitis occurred in Shandong province, China, starting from 1988. In 1989, 484 cases were recorded, which was the peak during the past 4 years. Although emergency immunization with trivalent oral poliovirus vaccine (OPV) was carried out in selected counties in 1989 and 1990, control of the outbreak was not satisfactory. OPV mass immunization campaigns were introduced to cover the whole province in early 1991, and the number of patients with paralytic poliomyelitis decreased to 95. In addition to this new immunization strategy, we began to construct new polio surveillance systems. These were a network for case-negative reporting and an immediate reporting system of acute flaccid paralysis (AFP). As for the case-negative reporting, presently more than 90% of counties have been reporting presence or absence of new AFP cases. Monitoring of AFP immediate reporting has also shown a gradual improvement in several aspects. These polio surveillance activities are crucial to polio eradication programme management.

Child↗