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Biomedical subjects

X Qi

Publications and source records attributed to X Qi.

At least 19 recordsLinked to original sources
PubMed2001

Mutation in Bmp7 exacerbates the phenotype of Bmp8a mutants in spermatogenesis and epididymis.

The specificity of bone morphogenetic proteins (BMPs) to their putative heteromeric receptor complexes in vivo is largely unclear. Closely related BMPs may use the same or different receptor complexes for signaling in a time- and space-dependent manner during development and differentiation. We have shown that Bmp7 expression in epididymal epithelium is developmentally regulated. Here, we further show that Bmp7 expression is also developmentally regulated in male germ cells. Bmp7 transcripts are detected in spermatogonia and early primary spermatocytes during early puberty and in stage-7 to -15 spermatids of the adult mice. Since Bmp7 homozygous mutants die perinatally and heterozygotes do not show obvious defects in the testis and the epididymis, the role of Bmp7 in spermatogenesis and epididymal function cannot be revealed by simply examining these mutants. Therefore, we have used a genetic approach by creating Bmp7/Bmp8a double mutants to investigate the role of Bmp7 in spermatogenesis and epididymal function. Here, we report that removal of one allele of Bmp7 exacerbates the phenotype of Bmp8a null mutants in spermatogenesis and epididymis of the adult. These indicate that, similar to Bmp8a, Bmp7 plays a role in both the maintenance of spermatogenesis and epididymal function and it further suggests that BMP8 and BMP7 signal through the same or similar receptors in these two systems.

Animals↗
PubMed2001

L-RCA (ligation-rolling circle amplification): a general method for genotyping of single nucleotide polymorphisms (SNPs).

A flexible, non-gel-based single nucleotide polymorphism (SNP) detection method is described. The method adopts thermostable ligation for allele discrimination and rolling circle amplification (RCA) for signal enhancement. Clear allelic discrimination was achieved after staining of the final reaction mixtures with Cybr-Gold and visualisation by UV illumination. The use of a compatible buffer system for all enzymes allows the reaction to be initiated and detected in the same tube or microplate well, so that the experiment can be scaled up easily for high-throughput detection. Only a small amount of DNA (i.e. 50 ng) is required per assay, and use of carefully designed short padlock probes coupled with generic primers and probes make the SNP detection cost effective. Biallelic assay by hybridisation of the RCA products with fluorescence dye-labelled probes is demonstrated, indicating that ligation-RCA (L-RCA) has potential for multiplexed assays.

Alleles↗
PubMed2001

A new class of oxidosqualene cyclases directs synthesis of antimicrobial phytoprotectants in monocots.

Many plants synthesize antimicrobial secondary metabolites as part of their normal program of growth and development, often sequestering them in tissues where they may protect against microbial attack. These include glycosylated triterpenoids (saponins), natural products that are exploited by man for a variety of purposes including use as drugs [Hostettmann, K. & Marston, A. (1995) Saponins (Cambridge Univ. Press, Cambridge, U.K.)]. Very little is known about the genes required for the synthesis of this important family of secondary metabolites in plants. Here we show the novel oxidosqualene cyclase AsbAS1 catalyzes the first committed step in the synthesis of antifungal triterpenoid saponins that accumulate in oat roots. We also demonstrate that two sodium azide-generated saponin-deficient mutants of oat, which define the Sad1 genetic complementation group, are defective in the gene encoding this enzyme and provide molecular genetic evidence indicating a direct link between AsbAS1, triterpenoid saponin biosynthesis, and disease resistance. Orthologs of AsbAS1 are absent from modern cereals and may have been lost during selection, raising the possibility that this gene could be exploited to enhance disease resistance in crop plants.

Amino Acid Sequence↗
PubMed2001

Gap junction blockers decrease defibrillation thresholds without changes in ventricular refractoriness in isolated rabbit hearts.

BACKGROUND: The maintenance and termination of reentry arrhythmias are determined by tissue properties such as refractoriness and conduction velocity. Although the effects of Na(+) and K(+) channel block on electrophysiological properties and defibrillation threshold (DFT) have been studied, little is known about the effect of gap junction blockers on defibrillation and tissue electrophysiological properties. METHODS AND RESULTS: Triplicate DFTs (volts) were obtained before and 15 minutes after 4 micromol/L 16-doxyl-stearic acid (16-DSA, n=8), 1 mmol/L 1-heptanol (n=12) (both gap junction blockers), 3 microg/mL lidocaine (a sodium channel blocker) (n=8), and respective controls (n=27) in isolated perfused rabbit hearts. DFT decreased after 16-DSA (23+/-14%, P<0.01) and 1-heptanol (21+/-16%, P<0.01) but increased after lidocaine (26+/-28%, P<0.05). Ventricular fibrillation cycle length (VFCL) and QRS duration increased after all 3 agents, by 36+/-19% and 44+/-16% (16-DSA), 87+/-42% and 49+/-15% (heptanol), and 57+/-20% and 43+/-26% (lidocaine), respectively (all P<0.01). Spatially averaged temporal VFCL dispersion decreased significantly after all 3 agents, by 47+/-42% (16-DSA, P<0.05), 74+/-19% (1-heptanol, P<0.01), and 82+/-13% (lidocaine, P<0.01), respectively. Ventricular effective refractory period and monophasic action potential duration at 90% repolarization were unchanged after 16-DSA and 1-heptanol (P=NS) but increased after lidocaine (16+/-13%, P<0.01, and 6+/-5%, P=NS, respectively). There were no significant changes in DFT or any other electrophysiological variable in control hearts. CONCLUSIONS: Electrical uncoupling by 16-DSA and 1-heptanol significantly lowers DFT and dispersion of VFCL without altering refractoriness; lidocaine, at doses resulting in similar slowing of conduction, increases DFT.

Animals↗
PubMed2001

Phospholipid membrane restructuring induced by saposin C: a topographic study using atomic force microscopy.

The enzymatic activity of glucosylceramidase depends on the presence of saposin C (Sap C) and acidic phospholipid-containing membranes. In order to delineate the mechanism underlying Sap C stimulation of the enzyme activity, it is important to understand how Sap C interacts with phospholipid membranes. We studied the dynamic process of Sap C interaction with planar phospholipid membranes, in real time, using atomic force microscopy (AFM). The phospholipid membrane underwent restructuring upon addition of Sap C. The topographic characteristics of the membrane restructuring include the appearance of patch-like new features, initially emerged at the edge of phospholipid membranes and extended laterally with time. Changes in the image contrast of the phospholipid membrane observed after the Sap C addition indicate that a new phase of lipid-protein structure has formed during membrane restructuring. The process of membrane restructuring is dynamic, commencing shortly after Sap C addition, and continuing throughout the duration of AFM imaging (about 30 min, sometimes over 1 h). This study demonstrated the potential of AFM real-time imaging in studying protein-membrane interactions.

Glycoproteins↗
PubMed2001

Induction of primordial germ cells from murine epiblasts by synergistic action of BMP4 and BMP8B signaling pathways.

Extraembryonic ectoderm-derived factors instruct the pluripotent epiblast cells to develop toward a restricted primordial germ cell (PGC) fate during murine gastrulation. Genes encoding Bmp4 of the Dpp class and Bmp8b of the 60A class are expressed in the extraembryonic ectoderm and targeted mutation of either results in severe defects in PGC formation. It has been shown that heterodimers of DPP and 60A classes of bone morphogenetic proteins (BMPs) are more potent than each homodimers in bone and mesoderm induction in vitro, suggesting that BMP4 and BMP8B may form heterodimers to induce PGCs. To investigate how BMP4 and BMP8B interact and signal for PGC induction, we cocultured epiblasts of embryonic day 6.0--6.25 embryos with BMP4 and BMP8B proteins produced by COS cells. Our data show that BMP4 or BMP8B homodimers alone cannot induce PGCs whereas they can in combination, providing evidence that two BMP pathways are simultaneously required for the generation of a given cell type in mammals and also providing a prototype method for PGC induction in vitro. Furthermore, the PGC defects of Bmp8b mutants can be rescued by BMP8B homodimers whereas BMP4 homodimers cannot mitigate the PGC defects of Bmp4 null mutants, suggesting that BMP4 proteins are also required for epiblast cells to gain germ-line competency before the synergistic action of BMP4 and BMP8B.

Animals↗
PubMed2001

Differential membrane interactions of saposins A and C: implications for the functional specificity.

Saposins are small, heat-stable glycoprotein activators of lysosomal glycosphingolipid hydrolases that derive from a single precursor, prosaposin, by proteolytic cleavage. Three of these saposins (B, C, and D) share common structural features including a lack of tryptophan, a single glycosylation sequence, the presence of three conserved disulfide bonds, and a common multiamphipathic helical bundle motif. Saposin A contains an additional glycosylation site and a single tryptophan. The oligosaccharides on saposins are not required for in vitro activation functions. Saposins A and C were produced in Escherichia coli to contain single tryptophans at various locations to serve as intrinsic fluorescence reporters, i.e. as topological probes, for interaction with phospholipid membranes. Maximum emission shifts, aqueous and solid quenching, and resonance energy transfer were quantified by fluorescence spectroscopy. Amphipathic helices at the amino- and carboxyl termini of saposins A and C were shown to insert into the lipid bilayer to about five carbon bond lengths. In comparison, the middle region of saposins A or C were either embedded in the bilayer or solvent-exposed, respectively. Conformational changes of saposin C induced by phosphatidylserine interaction suggested the reorientation of functional helical domains. Differential interaction models are proposed for the membrane-bound saposins A and C. By site-directed mutagenesis of saposin A and C, their membrane topological structures were correlated with their activation effects on acid beta-glucosidase. These findings show that proper orientation of the middle segment of saposin C to the outside of the membrane surface is critical for its specific and multivalent interaction with acid beta-glucosidase. Such membrane interactions and orientations of the saposins determine the proximity of their activation and/or binding sites to lysosomal hydrolases or lipoid substrates.

Amino Acid Sequence↗
PubMed2001

Vortex dynamics in superconducting MgB2 and prospects for applications.

The recently discovered superconductor magnesium diboride, MgB2, has a transition temperature, Tc, approaching 40 K, placing it intermediate between the families of low- and high-temperature superconductors. In practical applications, superconductors are permeated by quantized vortices of magnetic flux. When a supercurrent flows, there is dissipation of energy unless these vortices are 'pinned' in some way, and so inhibited from moving under the influence of the Lorentz force. Such vortex motion ultimately determines the critical current density, Jc, which the superconductor can support. Vortex behaviour has proved to be more complicated in high-temperature superconductors than in low-temperature superconductors and, although this has stimulated extensive theoretical and experimental research, it has also impeded applications. Here we describe the vortex behaviour in MgB2, as reflected in Jc and in the vortex creep rate, S, the latter being a measure of how fast the 'persistent' supercurrents decay. Our results show that naturally occurring grain boundaries are highly transparent to supercurrents, a desirable property which contrasts with the behaviour of the high-temperature superconductors. On the other hand, we observe a steep, practically deleterious decline in Jc with increasing magnetic field, which is likely to reflect the high degree of crystalline perfection in our samples, and hence a low vortex pinning energy.

Journal Article↗
PubMed2001

Genotype-dependent differences in S12-RNase expression lead to sporadic self-compatibility.

Sporadic self-compatibility, the occasional fruit formation after otherwise incompatible pollinations, has been observed in some S12-containing genotypes of Solanum chacoense but not in others. We have sequenced this S12 allele and analyzed its expression in four different genotypes. The S12-RNase levels were generally less abundant than those of other S-RNases present in the same plants. In addition, two-fold and five-fold differences in the amount of S12-RNase and S12 RNA, respectively, were observed among the genotypes analyzed. A comparison with the genetic data showed that genotypes with the highest levels were fully and permanently self-incompatible, whereas those with the lowest levels were those in which sporadic self-compatibility had been observed. The mature protein contains four potential glycosylation sites and genotype-specific differences in the pattern of glycosylation are also observed. Our results suggest the presence of modifier genes which affect, in a genotype-dependent manner, the level of expression and the post-translational modification of the S12-RNase.

Alleles↗
PubMed2001

Development of simple sequence repeat markers from bacterial artificial chromosomes without subcloning.

Simple sequence repeats (SSRs) were isolated from pearl millet bacterial artificial clones (BACs) without any subcloning steps. SSR sequences were targeted using 3' end-anchored SSR primers. Flanking sequences were isolated by suppression PCR. In this pilot study, 25 SSR markers have been developed from 40 BAC pools, comprising a total of 384 clones. This novel way to develop new markers has the added advantage that mapping the SSR markers will anchor individual BACs to the genetic maps and, thus, facilitate the construction of BAC contigs.

Chromosomes, Artificial, Bacterial↗
PubMed2001

[Experimental study in rabbit on repair of radial bone defect by bioactive degradable polymer].

OBJECTIVE: To investigate the availability of bone defect repair by degradable porous polycaprolactam (PCL) as the carrier of bone morphogenetic protein (BMP). METHODS: Three different kinds of bone substitutes, including decalcified bone matrix, PCL-BMP compounds and simple PCL, were implanted into the radial bone defects in 36 rabbits, and in the other 12 rabbits the bone defects were left untreated as control. X-ray examination, X-ray morphometry, histological and electron microscopic observation were performed at different time after operation. RESULTS: The quantity of new bone formation in PCL-BMP group was prior to that in simple PCL group. The pattern and speed of bone defect repair in PCL-BMP group were similar to those in decalcified bone matrix. Electron microscopic observation showed that the PCL-BMP group degraded faster than simple PCL group, which was more suitable for bone repair. CONCLUSION: PCL is a good carrier of BMP with potential for clinical use.

Animals↗
PubMed2000

Low-dimensional bose liquids: beyond the gross-pitaevskii approximation

The Gross-Pitaevskii approximation is a long-wavelength theory widely used to describe a variety of properties of dilute Bose condensates, in particular trapped alkali gases. We point out that for short-ranged repulsive interactions this theory fails in dimensions d</=2, and we propose the appropriate low-dimensional modifications, which have a universal form. For d = 1 we analyze density profiles in confining potentials, superfluid properties, solitons, and self-similar solutions.

Journal Article↗
PubMed2000

Infusion versus bolus of an ultrasound contrast agent: in vivo dose-response measurements of BR1.

RATIONALE AND OBJECTIVES: To determine the efficacy of an ultrasound contrast agent infusion using Doppler intensitometry estimation of backscatter enhancement in blood. METHODS: Multiple intravenous injections of BR1 (SonoVue) were performed in chronic dog studies, using bolus (0.05-2 mL) and infusion (3-40 mL/h during 6 minutes) administration. The pulsed Doppler signal from the femoral artery was recorded and analyzed for mean Doppler power and integrated fractional enhancement. RESULTS: For bolus injection, time-intensity curves exhibited a rapid first pass (peak 30 dB for 0.45 mL) followed by a slower washout. Integrated fractional enhancement exhibited a linear relation with the dose (R2 = 0.99). For infusion administration, peak enhancement increased with the infusion rate from 8 to 22 dB. At rates exceeding 30 mL/h, the enhancement was stable with a plateau-like pattern. CONCLUSIONS: Infusion of BR1 is easily achieved and allows the duration of enhancement to be increased as long as desired. Stable enhancement is obtained for rates greater than 30 mL/h.

Animals↗
PubMed2000

Saposins A, B, C, and D in plasma of patients with lysosomal storage disorders.

BACKGROUND: Early diagnosis of lysosomal storage disorders (LSDs), before the onset of irreversible pathology, will be critical for maximum efficacy of many current and proposed therapies. To search for potential markers of LSDs, we measured saposins A, B, C, and D in patients with these disorders. METHODS: Four time-delayed fluorescence immunoquantification assays were used to measure each of the saposins in plasma from 111 unaffected individuals and 334 LSD-affected individuals, representing 28 different disorders. RESULTS: Saposin A was increased above the 95th centile of the control population in 59% of LSD patients; saposins B, C, and D were increased in 25%, 61%, and 57%, respectively. Saposins were increased in patients from several LSD groups that in previous studies did not show an increase of lysosome-associated membrane protein-1 (LAMP-1). CONCLUSION: Saposins may be useful markers for LSDs when used in conjunction with LAMP-1.

Adolescent↗
PubMed2000

Hepatotropism of nonenveloped DNA virus in rhesus monkey infected by transfusion-transmitted virus.

OBJECTIVE: To study wether the nonenveloped DNA virus transmitted via blood transfusion is hepatotropic. METHODS: Total DNA was extracted from tissues of 5 experimentally infected Rhesus monkeys. A dot hybridization was done with virus double DNA strand probe or single antisense strand probe. RESULTS: Both single- and double-strand probes were hybridized with DNA of the liver, spleen, stomach, small intestine and colon. The virus was conformed present in most of all the organs when double-strand probe was used. The positive was noted only in the liver and small intestine when single-strand antisense probe was used, which showed that in liver and small intestine might have replicative intermediates of the virus. CONCLUSION: It suggests that nonenveloped DNA virus replicate in the liver and small intestine, so it might be hepatotropic.

Animals↗
PubMed2000

[Study on the inhibitory effect of antisense phosphorothioate oligodeoxynucleotide on coxsackie virus B replication in vitro].

OBJECTIVE: To investigate the antiviral effect of antisense phosphorothioate oligodeoxynucleotide (AODN) on CVB3 replication in vitro. METHODS: In this study, 21 mer antisense phosphorothioate oligodeoxynucleotide which complemented to nt 581-601 in 5' NCR of Coxsackie Virus B3 (CVB3) RNA was used to investigate antiviral activity in Vero cells as a specific inhibitor of CVB3 replication. Specific AODN of CVB3 RNA, sense oligodeoxynucleotide (SODN) and randomized nonsense-sequence RODN were synthesized for effect comparison among them. Vero cells infected by CVB3 were transfected with different concentrations of AODN mediated by lipofectamine reagent, so that the cells could take in more AODN. Cell control and viral control were set up. The inhibitory effect of AODN on CVB3 replication was evaluated with a number of variables, including inhibitory rates of cytopathic effect (CPE), cell survival rates by MTT assay, inhibitory rates of CVB3 antigen by ELISA, inhibitory rates of RNA by dot blotting and 50% tissue culture infective dose (TCID50). RESULTS: The specific AODN could significantly inhibit CPE of CVB3-infected Vero cells, decrease the production of antigen and RNA of CVB3 and viral titers, and increase cell survival rates, in a dose-dependent manner. The strongest inhibitory effect appeared at 48 hours after transfection, the most effective concentration of AODN was 10 micromol/L. On the other hand, 10 micromol/L SODN also showed weaker inhibitory effect on CPE of CVB3-infected cells, but no antiviral effect of 10 micromol/L RODN was shown. AODN showed no-inhibition on HSV-1 replication, but inhibited some enteroviruses such as CVB3, Polio-1 and Echo-6 to some extent. CONCLUSIONS: These results indicate that nt 581-601 in 5' NCR of CVB3 RNA may play an important role in regulating CVB3 replication and AODN may have inhibitory effect on CVB3 replication.

Animals↗
PubMed2000

[Analysis of the clinical characteristics and prognostic factors with primary normal-sized epithelial ovarian carcinoma syndrome].

OBJECTIVE: To investigate the clinical characteristics and prognostic factors of the primary normal-sized epithelial ovarian carcinoma syndrome. METHODS: The clinical records and pathologic slides of the 10 patients who satisfied the diagnostic criteria were retrospectively analyzed. RESULTS: The primary normal-sized epithelial ovarian carcinoma syndrome was detected in approximately 1.92% of the patients with the epithelial ovarian carcinoma. The age of the patients at diagnosis ranged from 43-70 years, with a median age of 57 years. The most common presentations included anorexia, increasing abdominal girth and awareness of abdominal or pelvic mass. During the exploratory laparotomy although we often discovered the diffuse metastasis throughout the abdominal and pelvic cavity, the ovaries both appeared normal size and had a fine granularity on the external surface. The survival time of patients with remained tumors smaller than 2.0 cm was longer than those with remained tumors larger than 2.0 cm, but the Log-rank evaluation indicated chi 2 = 0.61, P > 0.05. The patients who underwent postoperative chemotherapy have been noted to achieve some long-term survival. The median survival time was 20 months. CONCLUSION: The results predict that the size of the remained tumors may be one of the important factors to the survival and the disease is sensitive to the postoperative chemotherapy.

Adult↗