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Biomedical subjects

S Y Xu

Publications and source records attributed to S Y Xu.

At least 37 records · Page 2Linked to original sources

User acceptability of a female condom (Reality) in Shanghai.

Thirty married couples evaluated the Reality female condom on questionnaires about its acceptability for 300 acts of coitus (10 per couple). An analysis of the summary questionnaires showed: 90% of couples considered the female condom an acceptable method and 87% felt it was a good contraceptive device; the majority of couples (87%) found it easy to use; and 80% of females and 73% of males reported that, in comparison with the male condom, the effect on sexual pleasure was either improved or no different. A little more than half of the couples (55%) preferred it to male condoms. To look at the learning curve effect, an additional analysis was completed by pooling the first 5 applications of each user and comparing the results with the pooled results of the second 5 uses. All the findings suggest that a certain proportion of couples of childbearing age will choose the Reality female condom for contraception if it enters into the Chinese market. As a new contraceptive barrier device, the female condom may require a certain amount of education and awareness before it will be fully recognized as an important option to help prevent pregnancy as well as sexually transmitted infections.

Adult↗

The Tsp45I restriction-modification system is plasmid-borne within its thermophilic host.

Thermus species YS45 harbors two small cryptic plasmids of 5.8 (pTsp45s) and approximately 12 kb (pTsp45I). Plasmid pTsp45s has been entirely sequenced, revealing three significant ORFs. In addition to a previously reported thermophilic plasmid-encoded replication protein (Rep), pTsp45s contains two genes for the Tsp45I methyltransferase (M.Tsp45I) and restriction endonuclease (Tsp45I). These two converging genes (tsp45IM and tsp45IR) overlap by 4 bp at their stop codons within an XbaI site. M.Tsp45I (413 aa, 47.0 kDa, recognizing 5'-GTSAC-3') is highly homologous to other m6A-methyltransferases, especially M.EcaI (recognizing 5'-GGTNACC-3'). Tsp45I (332 aa, 37.4 kDa, cleaving 5'-/GTSAC-3') is not homologous to M.Tsp45I, or to other restriction endonucleases. Recombinant Tsp45I is stably produced in E. coli, and cleaves DNA at 65 degrees C with the same specificity as the native enzyme. Therefore, the thermophilic Tsp45I restriction-modification system is plasmid-borne within its native host.

Amino Acid Sequence↗

Identification of a thermophilic plasmid origin and its cloning within a new Thermus-E. coli shuttle vector.

A pUC19-based vector has been generated for selecting functional thermophilic origins (oris) of Thermus ssp. Once combined with thermophilic DNA, the vector can be amplified in ampicillin resistant (Ap(R)) E. coli, prior to transformation and kanamycin (Km) selection in Thermus thermophilus. The Km(R) Thermus transformants replicate any newly-formed shuttle vectors via introduced thermophilic oris. Using this "ori-selecting" vector, three novel thermophilic oris were cloned from randomly digested Thermus cryptic plasmid DNA. These shuttle vectors are useful for genetic analyses, as well as protein engineering within thermophiles. The smallest ori-containing sequence of 4.2 kb has been subcloned, sequenced, and further refined to 2.3 kb. A significant ORF of 341 amino acids (aa), with a Thermus promoter and RBS, is found within the thermophilic ori. Deleting part of this ORF abolishes the shuttle vector's ability to replicate in T. thermophilus. Therefore, we postulate that this ORF encodes a replication protein (Rep) necessary for thermophilic plasmid replication. The thermophilic ori also contains two sequences which resemble DnaA boxes.

Amino Acid Sequence↗

Molecular cloning and expression of NlaIII restriction-modification system in E. coli.

The NlaIII restriction enzyme isolated from Neisseria lactamica recognizes the sequence 5'-CATG-3', cleaving after the G to generate a four base 3' overhang. The NlaIII methylase and a portion of the NlaIII endonuclease gene were cloned into E. coli by the methylase selection method, and the remaining portion of the NlaIII endonuclease gene was cloned by inverse PCR. The nucleotide sequence of the endonuclease gene and the methylase gene were determined. The NlaIII endonuclease gene is 693 bp, encoding a protein with predicted molecular weight of 26487. The NlaIII methylase gene was identical with that previously reported [Labbe, D., Joltke, H.J. and Lau, P.C. (1990) Cloning and characterization of two tandemly arranged DNA methyltransferse genes of Neisseria lactamica: an adenine-specific M.NlaIII and a cytosine-type methylase. Mol. Gen. Genet. 224, 101-110]. The endonuclease and methylase genes overlap by four bases and are transcribed in the same orientation. The endonuclease gene was cloned into an improved T7 vector, and a high level of NlaIII endonuclease expression was achieved in E. coli.

Amino Acid Sequence↗

Cloning and sequence comparison of AvaI and BsoBI restriction-modification systems.

AvaI and BsoBI restriction endonucleases are isoschizomers which recognize the symmetric sequence 5'CYCGRG3' and cleave between the first C and second Y to generate a four-base 5' extension. The AvaI restriction endonuclease gene (avaIR) and methylase gene (avaIM) were cloned into Escherichia coli by the methylase selection method. The BsoBI restriction endonuclease gene (bsoBIR) and part of the BsoBI methylase gene (bsoBIM) were cloned by the "endo-blue" method (SOS induction assay), and the remainder of bsoBIM was cloned by inverse PCR. The nucleotide sequences of the two restriction-modification (RM) systems were determined. Comparisons of the predicted amino acid sequences indicated that AvaI and BsoBI endonucleases share 55% identity, whereas the two methylases share 41% identity. Although the two systems show similarity in protein sequence, their gene organization differs. The avaIM gene precedes avaIR in the AvaI RM system, while the bsoBI R gene is located upstream of bsoBI M in the BsoBI RM system. Both AvaI and BsoBI methylases contain motifs conserved among the N4 cytosine methylases.

Amino Acid Sequence↗

Genetic mapping of RP1 on 8q11-q21 in an Australian family with autosomal dominant retinitis pigmentosa reduces the critical region to 4 cM between D8S601 and D8S285.

The locus (RP1) for one form of autosomal dominant retinitis pigmentosa (adRP) was mapped on chromosome 8q11-q22 between D8S589 and D8S285, which are about 8 cM apart, by linkage analysis in an extended family ascertained in the USA. We have studied a multigeneration Australian family with adRP and found close linkage without recombination between the disease locus and D8S591, D8S566, and D8S166 (Zmax = 1.137-4.650 at theta = 0.00), all mapped in the region known to harbor RP1. Assuming that the mutation of the same gene is responsible for the disease in both families, the analysis of multiply informative meioses in the American and Australian families places the adRP locus between D8S601 and D8S285, which reduces the critical region to about 4 cM, corresponding to approximately 4 Mb, which is completely covered by a yeast artificial chromosome contig assembled recently.

Adult↗

A ninth locus (RP18) for autosomal dominant retinitis pigmentosa maps in the pericentromeric region of chromosome 1.

We studied a large Danish family of seven generations in which autosomal dominant retinitis pigmentosa (adRP), a heterogeneous genetic form of retinal dystrophy, was segregating. After linkage had been excluded to all known adRP loci on chromosomes 3q, 6p, 7p, 7q, 8q, 17p, 17q and 19q, a genome screening was performed. Positive lod scores suggestive of linkage with values ranging between Z = 1.58-5.36 at theta = 0.04-0.20 were obtained for eight loci on proximal 1p and 1q. Close linkage without recombination and a maximum lod score of 7.22 at theta = 0.00 was found between the adRP locus (RP18) in this family and D1S498 which is on 1q very near the centromere. Analysis of multiply informative meioses suggests that in this family D1S534 and D1S305 flank RP18 in interval 1p13-q23. No linkage has been found to loci from this chromosomal region in six other medium sized adRP families in which the disease locus has been excluded from all known chromosomal regions harbouring an adRP gene or locus suggesting that there is (at least) one further adRP locus to be mapped in the future.

Base Sequence↗

Pharmacokinetics of m-nifedipine in rabbits after intravenous injection.

AIM: To study the dose effects on pharmacokinetics of m-Nif. METHODS: Fifteen rabbits were divided into 3 groups receiving i.v. m-Nif 0.5, 1, and 2 mg.kg-1. Plasma levels of m-Nif were determined with HPLC method. RESULTS: The concentration-time data were fitted with 2-compartment model. After i.v. 1 mg.kg-1, the parameters were: Vd = 0.37 +/- 0.10 L.kg-1, T1/2 alpha = 6.4 +/- 2.9 min, T1/2 beta = 84 +/- 22 min, AUC = 94 +/- 16 mg.min.L-1, Cl = 0.65 +/- 0.13 L.kg-1.h-1. No statistically significant difference was found in Cl and T1/2 beta between 3 dose groups. AUC (standardized to body weight) was correlated with doses. CONCLUSIONS: m-Nif was distributed widely and eliminated at a fairly rapid rate in the rabbits. No dose-dependent pharmacokinetics was found after i.v. m-Nif 0.5-2 mg.kg-1. m-Nifedipine, 2, 6-dimethyl-3, 5-dicarbomethoxy-4-(3'-nitrophenyl)-1, 4-dihydropyridine (m-Nif) is a new calcium channel blocker. Dihydropyridine calcium channel antagonists are mainly used for the treatment of hypertension and angina[1]. Nifedipine is susceptible to photodegradation, but m-Nif is stable when exposed to light. The 2 drugs have the same antihypertensive effect[2]. So far, no report has been found on pharmacokinetics of m-Nif. Using a high performance liquid chromatographic (HPLC) method, we studied the dose effects on the pharmacokinetics of i.v. m-Nif 0.5, 1, and 2 mg.kg-1 in conscious rabbits.

Animals↗

Protective effect of hyperin against myocardial ischemia and reperfusion injury.

AIM: To study the protective and antiperoxidative effects of hyperin (hyperoside; quercetin-3-O-galactoside; Hyp) on myocardial ischemia/reperfusion. METHODS: The rabbit anterior descenging branch of left coronary artery was occluded for 60 min and then released to allow reperfusion for 20 min. Hemodynamics (LVP, LV +/- dp/dt) and electrocardiogram (ECG, lead II) were monitored continuously with polygraph. After reperfusion, the blood sample and myocardium were taken to assay plasma creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and cations in myocardium. Using a Langendorff system, the isolated heart of rat was initiated by ischemia for 40 min followed by 30 min of reperfusion. Malondialdehyde (MDA) contents of cardiac effluent and myocardium were measured with fluorescence spectrophotometer. RESULTS: Hyp 10 mg.kg-1 i.v. depressed changes in LVP, LV +/- dp/dtmax, ECG, plasma CPK, LDH, and cations (Ca2+, Mg2+, Na+) in myocardium induced by ischemia/reperfusion in rabbits. Hyp 10 and 100 mumol.L-1 markedly reduced the increase in MDA production in isolated rat hearts after ischemia/reperfusion. CONCLUSION: Hyp possesses a protective effect against myocardial ischemia/reperfusion injury via attenuating lipid peroxidation.

Animals↗

Cloning of a gene from Thermus filiformis and characterization of the thermostable nuclease.

A gene coding for a thermostable nuclease was cloned from the thermophilic microorganism, Thermus filiformis (Tf), using an indicator strain containing a dinD::lacZ fusion. The gene, designated nuc17, has been mapped within a 2300-bp fragment. The 55-kDa Tf nuclease was purified to over 95% homogeneity. Single-stranded (ss) DNA is the preferred substrate for the Tf nuclease, although double-stranded (ds) DNA can also be digested. Nuclease activity increases with increasing temperature up to 80 degrees C and requires the metal ions Ca++ or Mg++ for catalysis. Tf nuclease is primarily an endonuclease that leaves 5' phosphates in the digested products. The ssDNA extensions remaining after exonuclease III digestion of dsDNA can be removed by the Tf nuclease, making it a useful reagent to generate unidirectional deletions.

Bacterial Proteins↗

Nucleotide sequence of a small plasmid isolated from Acetobacter pasteurianus.

A 1440-bp plasmid named pAP12875 was isolated from Acetobacter pasteurianus and its nucleotide sequence determined. An open reading frame was found capable of coding for a protein that has similarity with the replication protein of pVT736-1 from Actinobacillus actinomycetemcomitans and the 32-kDa protein of phage Pf3 from Pseudomonas aeruginosa.

Acetobacter↗

Isolation of temperature-sensitive mutants of the BamHI restriction endonuclease.

Two heat-sensitive R.BamHI mutants, T157I and P173L, and one cold-sensitive R.BamHI mutant, T114I, were isolated after chemical mutagenesis of the bamhIR gene that codes for the restriction endonuclease BamHI (R.BamHI). The thermosensitivity of T114I, T157I and P173L is revealed by the 10(2)-10(3) lower plating efficiency at the non-permissive temperature of strains bearing these alleles. The conditional-lethal phenotype can be rescued by introduction of the cognate bamhIM gene into the same cell. The mutant enzymes induce the SOS response in vivo and display reduced phage restriction activity. The P173L protein, when expressed at 30 degrees C and purified, shows reduced thermostability at 65 degrees C. T157I and P173L mutants yield different intermediates during partial trypsin digestion. The conditional-lethal BamHI mutants could be used to deliver in vivo DNA cleavage and for further isolation of relaxed-specificity mutants.

Amino Acid Sequence↗

Serum measurements of human neutrophil lipocalin (HNL) discriminate between acute bacterial and viral infections.

Human neutrophil lipocalin (HNL) is a recently identified protein from human neutrophil granules. The concentrations of HNL in the circulation were measured, in a group of patients with acute infections, using a radioimmunoassay. The concentrations of HNL in patients infected by viruses and bacteria were 93.78 +/- 45.30 micrograms l-1 (SD), 404.14 +/- 355.02 micrograms l-1 (SD) in serum, and 47.81 +/- 18.18 micrograms l-1 (SD), 145.46 +/- 194.32 micrograms l-1 (SD) in plasma, respectively. The differences between the two patient groups were highly significant. There was a significant correlation between serum HNL and plasma HNL levels in bacterial infections (r = 0.73, p < 0.0001). The HNL serum levels also correlated with those of C-reactive protein (CRP) (r = 0.59, p < 0.0001). Determination of HNL in serum was more specific and sensitive than CRP in the distinction between viral and bacterial infections. At a cut-off of 155 micrograms l-1 (HNL in serum), the positive and negative predictive values for the diagnosis of bacterial infections were 92 and 96%, respectively, which were superior to the optimal predictive values of CRP. Thus, the determination of HNL level is useful in the diagnosis of acute bacterial infections.

Acute-Phase Proteins↗

Effects of pineal body and melatonin on lymphocyte proliferation and dinoprostone production in rat spleen.

AIM: To determine the effects of pineal body and melatonin (Mel) on lymphocyte proliferation and dinoprostone production in rat spleen. METHODS: Pinealectomy (PE), lymphocyte proliferation assay and dinoprostone radioimmunoassay were used. RESULTS: A circadian rhythm of splenic lymphocyte proliferation which peaked at 22:00 was obliterated by PE in rats. PE led to an impairment of lymphocyte proliferation and an increase of dinoprostone production, which were restored by ip Mel 10 micrograms.kg-1.d-1 at 16:00 for 7 d. Mel promoted lymphocyte proliferation and inhibited dinoprostone production in intact rats. A negative correlation between the change in lymphocyte proliferation and dinoprostone production was seen. CONCLUSION: The pineal body and its main hormone Mel play a regulatory role in circadian lymphocyte proliferation which is related to dinoprostone production in rat spleen.

Animals↗

Effect of pineal body and melatonin on chemiluminescence of peritoneal macrophages via hypothalamus in rats.

AIM: To study whether the hypothalamus was a major relay for the action of melatonin (Mel) on peritoneal macrophage (PM subliminal diameter of) function. METHODS: Pinealectomy, luminol-dependent chemiluminescence (CL), hypothalamic dinoprostone radioimmunoassay, and intrahypothalamic injection of Mel were done in rats kept under light:dark 12h:12h. RESULTS: CL value of PM subliminal diameter of was decreased and hypothalamic dinoprostone content was elevated after pinealectomy, which were restored by Mel (10 micrograms kg-1 d-1 ip at 16:00 for 7 d). The same treatment of Mel increased CL value of PM subliminal diameter of and depressed hypothalamic dinoprostone production in intact rats. CL value of PM subliminal diameter of showed negative relation to hypothalamic dinoprostone with r = -0.78 (P < 0.01). Intrahypothalamic injection of Mel (2 micrograms) enhanced CL value of PM subliminal diameter of in normal and pinealectomized rats. CONCLUSION: The hypothalamus is a main site of pineal Mel action upon PM subliminal diameter of function.

Adjuvants, Immunologic↗

The 'endo-blue method' for direct cloning of restriction endonuclease genes in E. coli.

A new E. coli strain has been constructed that contains the dinD1::LacZ+ fusion and is deficient in methylation-dependent restriction systems (McrA-, McrBC-, Mrr-). This strain has been used to clone restriction endonuclease genes directly into E. coli. When E. coli cells are not fully protected by the cognate methylase, the restriction enzyme damages the DNA in vivo and induces the SOS response. The SOS-induced cells form blue colonies on indicator plates containing X-gal. Using this method the genes coding for the thermostable restriction enzymes Taql (5'TCGA3') and Tth111l (5'GACNNNGTC3') have been successfully cloned in E. coli. The new strain will be useful to clone other genes involved in DNA metabolism.

Base Sequence↗

The development of an assay for human neutrophil lipocalin (HNL)--to be used as a specific marker of neutrophil activity in vivo and vitro.

Human neutrophil lipocalin (HNL) is a newly discovered protein from human neutrophil secretory granules. A double-antibody radioimmunoassay (RIA) was developed for the measurement of HNL in various body fluids and its high specificity was confirmed by the absence of cross-reaction with other granulocyte granule proteins. The RIA measures HNL within the range of 4-256 micrograms/l. The intra- and interassay coefficients of variation were less than 6% and 10%, respectively. When HNL was added to serum samples full recovery was obtained. Sera and plasma from 100 apparently healthy individuals revealed a mean level of 78.40 micrograms/l (range 37.95-190.87 micrograms/l) in serum and a mean level of 50.65 micrograms/l (range 30.51-105.8 micrograms/l) in EDTA-plasma. The distribution of HNL after gel filtration indicated that HNL exists mainly in two major forms, dimer and monomer. This, in addition to the excellent recovery, suggests that these major forms of HNL do not bind to compounds in serum or plasma that would interfere with the assay. The high specificity, sensitivity, reproducibility and accuracy of the present assay should facilitate the measurement of HNL in blood and other body fluids.

Acute-Phase Proteins↗