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Biomedical subjects

B Xu

Publications and source records attributed to B Xu.

At least 271 records · Page 15Linked to original sources
PubMed1996

[Coronary angiographic characteristics of patients with unstable angina].

In order to study the characteristics of coronary lesions of patients with unstable angina, coronary angiograms and clinical manifestations were analysed on 388 patients. The results were as follows: single vessele disease was more common in new onset effort angina (69.64%) than in other groups (P < 0.05). Triple vessele disease and left main coronary artery lesion appeared more frequently in patients with rest angina than in other groups (72.34% and 27.66% respectively, P < 0.05), so did complex lesions and type C lesions (36.07% and 60.64% respectively, P < 0.05). More than half of the culprit lesions in early postinfarction angina was subtotal or total occlusions (53.12%), being more frequently found in this than in other groups (P < 0.05). Most of the patients with Prinzmetal variant angina had mild coronary lesions only. Coronary thrombi were found in 10.45% of the 388 patients; they were was more frequent in patients with early postinfarction angina (20.00%) than in the groups of new onset effort angina, aggravated effort angina and Prinzmetal variant angina (4.26%, 7.53% and 0% respectively, P < 0.05). Coronary thrombi were also more frequent in the patients with chest pain at rest (16.39%) than in the groups of new onset effort angina and Prinzmetal variant angina (P < 0.05). It is suggested that patients with angina at rest should be treated more intensively. Strengthened anticoagulation treatment should be given to patients with early postinfarction angina and angina at rest.

Adult↗
PubMed1996

[Detection of immunoglobulin heavy chain (IgH) gene rearrangement in ANLL by polymerase chain reaction amplification and Southern blot].

Immunoglobulin heavy chain (IgH) gene rearrangement serves as a marker of clonality in B lymphoproliferative malignancies. In order to study the IgH rearranged gene in acute nonlymphoblastic leukemia (ANLL) patients we combine polymerase chain reaction (PCR) with Southern blot to detect 41 ANLL patients and 7 of them (17.1%) were found to have IgH rearrangement by PCR amplification. All these 7 positive cases were confirmed by Southern blot. The sensitivity of this method was 10(-4)-10(-5) level. In 12 patients with complete remission, 3 (25.0%) were found to have IgH rearranged gene. All these 3 cases had clinical relapse within 6 months. Our results show that IgH rearrangement not only may occur in lymphoblastic leukemia of B lineage, but also can be found in ANLL. The mechanism may be that in some ANLL patients, the leukemic transforming event might involve stem cells capable of both B cell and myeloid differentiation or ANLL might differentiate along different lineage with predominant appearance of one or the other subclone in the course of the disease.

Blotting, Southern↗
PubMed1996

[Stability of jingu tongxial pills].

The stability of Jingu Tongxiao Pills was studied on the basis of accelerated destruction and sample-reserving observation at room temperature. According to the changes of tanshinone IIA in the sample, the time of efficacy determined by the two methods is 1.89 and 2.30 years respectively. Based on the analysis of other indices, the effective period is tentatively determined as two years.

Abietanes↗
PubMed1996

Induction of apoptosis in human leukemia K562 cells by alpha-anordrin.

AIM: To study antitumor action of alpha-anordrin (Ano). METHODS: Morphological assessment of apoptosis was performed with light microscope and electron microscope. Membrane integrity was determined by trypan blue exclusion method. Endonucleolysis was assessed by agarose gel electrophoresis and flow cytometric methods. RESULTS: Exposure of exponentially growing K562 cells to Ano 2.5-50 mumol.L-1 for 48 h resulted in growth arrest, Ano 50 mumol.L-1 inhibited the growth of K562 cells by 67%. Cells were mainly blocked to progress through S-phase and arrested at G1 phase. After treatment of K562 cells with Ano, marked morphological changes including condensed chromatin, nuclear fragmentation, and reduction in volume were observed. Agarose gel electrophoresis of DNA from cells treated with Ano for 24-48 h revealed "ladder" pattern, typical features of apoptosis, and near 70% of cells underwent apoptosis as determined by flow cytometry. The S-phase cells were more susceptible to apoptosis. Despite extensive cleavage of DNA and nuclear fragmentation, the cell membrane of Ano-treated cells remained intact, excluding trypan blue. Apoptotic cells were detected as early as 8 h after Ano (50 mumol.L-1) treatment. CONCLUSION: Ano induces apoptosis in K562 cells.

Antineoplastic Agents↗
PubMed1996

[(Sp)-8-chloroadenosine 3',5'-cyclophosphate induced differentiation on human leukemia HL-60 cells].

(Sp)-octyl 8-chloroadenosine 3',5'-cyclophosphate(OCC), a newly synthesized cAMP analog, strongly induced growth inhibition and differentiation in human leukemia HL-60 cells. The effects were dose- and time-dependent and irreversible. In flow cytometry, OCC brought about a block at the G1 phase of HL-60 cell cycle. Determined by incorporation assay, OCC was shown to strongly inhibit DNA synthesis without affecting the synthesis of RNA and protein in HL-60 cells. OCC activated the protein kinase A(PKA) in the cytosol of HL-60 cells and inhibited its binding to cAMP. The activities of PKA in the cytosol of HL-60 cells treated with OCC were more significantly increased than those in control cells. It can be concluded that OCC binds itself to PKA in competition with cAMP and, as a result, activates PKA.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Substrate specificities of the insulin and insulin-like growth factor 1 receptor tyrosine kinase catalytic domains.

To compare the substrate specificities of the insulin and insulin-like growth factor 1 (IGF-1) receptor tyrosine kinases, the catalytic domains of the enzymes have been expressed in Escherichia coli as fusion proteins. The purified proteins have kinase activity, demonstrating that the catalytic domain of IGF-1 receptor, like that of insulin receptor, is active independent of its ligand-binding and transmembrane domains. The specificities of the two enzymes for the divalent cations Mg2+ and Mn2+ are indistinguishable. A series of peptides has been prepared that reproduces the major phosphorylation sites of insulin receptor substrate-1, a common substrate for the two receptor tyrosine kinases in vivo. Insulin and IGF-1 receptors show distinct preferences for these peptides; whereas insulin receptor prefers peptides based on Tyr-987 or Tyr-727 of insulin receptor substrate-1, the IGF-1 receptor preferentially recognizes the Tyr-895 site. The latter site, when phosphorylated, is a binding site for the SH2 domain-containing adapter protein Grb2. The ability of the two receptor tyrosine kinases to be phosphorylated and activated by v-Src has also been examined. The catalytic activity of IGF-1 receptor is stimulated approximately 3.4-fold by treatment with purified v-Src, while insulin receptor shows very little effect of Src phosphorylation under these conditions. This observation is relevant to recent findings of IGF-1 receptor activation in Src-transformed cells, and may represent one method by which Src amplifies its mitogenic signal. Collectively the data suggest that the catalytic domains of the two receptor kinases possess inherently different substrate specificities and signaling potentials.

Amino Acid Sequence↗
PubMed1995

Neuropeptide Y injection into the fourth cerebroventricle stimulates c-Fos expression in the paraventricular nucleus and other nuclei in the forebrain: effect of food consumption.

Injection of neuropeptide Y (NPY) into the cerebroventricular system of the rat results in a robust feeding response. In this study, we observed that NPY injection into the fourth ventricle augmented feeding and Fos-like immunoreactivity (FLI) in the paraventricular nucleus (PVN) and in other neighboring nuclei in the forebrain previously implicated in stimulation of feeding. Since the rostral transport of NPY in cerebrospinal fluid after injection into the fourth ventricle is unlikely and the topography of FLI as well as feeding behavior seen in this study are similar to those observed previously after NPY injection into the lateral cerebroventricle, these findings are in accord with the view that feeding induced by NPY injection into the fourth ventricle may also be mediated by NPY receptive elements in the forebrain.

Analysis of Variance↗
PubMed1995

Efficient incorporation of anti-HIV deoxynucleotides by recombinant yeast mitochondrial DNA polymerase.

Saccharomyces cerevisiae mtDNA polymerase, isolated as a single 135-kDa recombinant polypeptide, showed high processivity and a capacity of use poly(dA).oligo(dT), poly(rA).oligo(dT), or primed bacteriophage M13 DNA as a template. In a primer extension assay, the enzyme exhibited an intrinsic 3'-5'-exonuclease activity. By optimizing the polymerization reaction conditions, apparent Km and Vmax values could be determined for the incorporation of dTTP, 2'-3'-dideoxy-TTP (ddTTP), 3'-azido-TTP (AZTTP), 3'-fluoro-TTP, dCTP, 2'-3'-dideoxy-CTP, and didehydro(d4)CTP. The yeast mtDNA polymerase used ddTTP, 3'-fluoro-TTP, and ddCTP almost as efficiently as natural deoxynucleoside trisphosphates. Both 3'AZTTP and d4CTP were each significantly less efficient as substrates. Overall, the kinetic data with mtDNA polymerase were very similar to those of the recombinant human immunodeficiency virus reverse transcriptase control. Terminally incorporated AZTTP or ddTTP was not removed by the 3'-5' exonuclease activity of mtDNA polymerase. This may explain the inhibition of mtDNA replication observed in anti-human immunodeficiency virus treatment with dideoxynucleoside analogs for their effects of mtDNA polymerase could be of value in future rational drug design.

Antiviral Agents↗
PubMed1995

Evaluation of twin growth status at birth using individualized growth assessment: comparison with conventional methods.

OBJECTIVE: We sought to evaluate the growth status of twins at birth using individualized growth assessment methods and to compare this assessment with that obtained with conventional methods. STUDY DESIGN: Twenty twin pregnancies were studied longitudinally with ultrasound. Measurements of the head and abdominal cubes (A,B), head circumference (HC), abdominal circumference (AC), thigh circumference (ThC), and femur diaphysis length (FDL) made in the 2nd trimester were used to specify Rossavik growth models for each parameter in each fetus. These models were used to predict weight (WT), HC, AC, ThC, and crown-head length (CHL) at birth. Actual birth measurements made within 24 hours of delivery were compared to predicted values, the latter corrected using singleton [corrects for both technical problems (TP)] or twin [corrects for both technical problems (TP) and decreased soft-tissue deposition (DSTD)] correction factors where appropriate. Two sets of growth potential realization index (GPRI) values and their corresponding neonatal growth assessment scores (NGAS) were calculated and compared to previously established normal values. Birth measurements were compared with appropriate population age-specific size curves. These data were used to characterize and classify the growth status of each twin neonate. RESULTS: Individualized growth assessment identified five primary types of growth outcomes: normal (Group I, 45%); primarily DSTD (Group II, 22.5%); IUGR (Group III, 15%); above average soft-tissue deposition (Group IV, 5%); and growth acceleration (Group V, 7.5%). Within Group I was a subgroup with evidence of DSTD (Group Ib, 33.3% of Group I). Group II could be divided into two subgroups, one with only DSTD (Group IIa, 44.4% of Group II) and one with both DSTD and other growth abnormalities (Group IIb, 55.6% of Group II). Group III had multiple growth abnormalities which were more severe than those seen in Group II. All normal neonates were AGA and had virtually all anatomic parameters within their respective normal ranges. Of the neonates with definite evidence of IUGR (Groups IIb and III), only 4 of 11 (36.4%) were SGA and only 6 of 11 (54.5%) had any of the five anatomic parameters below their respective normal ranges. Only 1 of 3 (33.3%) of neonates with growth acceleration was LGA and none (0%) of the five anatomic parameters were above their respective normal ranges. CONCLUSIONS: Individualized growth assessment methods provide a more comprehensive assessment of growth outcome in twins and detect a decrease in soft-tissue deposition not identifiable with conventional growth assessment procedures. The latter procedures are also less sensitive in the detection of both IUGR and growth acceleration.

Adolescent↗
PubMed1995

Tests for possible effects of selection by domestic pyrethroids for resistance in culicine and anopheline mosquitoes in Sichuan and Hubei, China.

Resistance tests, by conventional methods and by observing the time for knockdown, showed no evidence for any build up of resistance to deltamethrin in malaria vectors from areas where millions of bednets have been treated with this compound annually for up to 7 years. However, a strain of Culex quinquefasciatus which had been bred in a factory in which volatile pyrethroids are handled had developed unequivocal resistance to deltamethrin. Observation of the time for knockdown gave clearer discrimination between resistant and susceptible strains than did observation of percentage mortality after a standard exposure time.

Animals↗
PubMed1995

Differential transcription of baculovirus late and very late promoters: fractionation of nuclear extracts by phosphocellulose chromatography.

An in vitro transcription system based on cytidine-free cassette was developed for the late 39k gene and the very late polyhedrin gene of Autographa californica nuclear polyhedrosis virus (AcNPV). Optimization of transcription conditions revealed that a preincubation step was not required for transcription of late and very late promoters, although preincubation was essential for efficient transcription from an early promoter. The 39k and polyhedrin constructs were actively transcribed by nuclear extracts prepared from AcNPV-infected Spodoptera frugiperda cells at 12 or 36 h postinfection but not by nuclear extracts prepared from uninfected or infected cells harvested during the early phase of infection. Transcription from the very late polyhedrin promoter was fivefold higher than that from the 39k late promoter with the nuclear extract prepared at 36 h postinfection. The 36-h extract was fractionated by phosphocellulose chromatography. Transcription activity eluted in two fractions, at 0.3 and 0.5 M KCl. Both the 39k and polyhedrin constructs were transcribed by these fractions; however, the patterns of late and very late transcription were distinctly different. With the 0.3 M fraction, incorporation into the 39k transcript was approximately 10-fold higher than incorporation into the polyhedrin transcript. Alternatively, with the 0.5 M fraction, transcription of the polyhedrin construct was twofold higher than transcription of the 39k construct. These results indicate that this in vitro system will be useful for purification and identification of factors that discriminate between late and very late promoters.

Animals↗
PubMed1995

A persistent RNA-DNA hybrid is formed during transcription at a phylogenetically conserved mitochondrial DNA sequence.

Critical features of the mitochondrial leading-strand DNA replication origin are conserved from Saccharomyces cerevisiae to humans. These include a promoter and a downstream GC-rich sequence block (CSBII) that encodes rGs within the primer RNA. During in vitro transcription at yeast mitochondrial replication origins, there is stable and persistent RNA-DNA hybrid formation that begins at the 5' end of the rG region. The short rG-dC sequence is the necessary and sufficient nucleic acid element for establishing stable hybrids, and the presence of rGs within the RNA strand of the RNA-DNA hybrid is required. The efficiency of hybrid formation depends on the length of RNA synthesized 5' to CSBII and the type of RNA polymerase employed. Once made, the RNA strand of an RNA-DNA hybrid can serve as an effective primer for mitochondrial DNA polymerase. These results reveal a new mechanism for persistent RNA-DNA hybrid formation and suggest a step in priming mitochondrial DNA replication that requires both mitochondrial RNA polymerase and an rG-dC sequence-specific event to form an extensive RNA-DNA hybrid.

Base Sequence↗
PubMed1995

Serogroup conversion of Vibrio cholerae.

Vibrio cholerae serogroup O1 can be detected in the environment in a viable but nonculturable form, whereas V. cholerae non-O1 cells can be readily cultured during interepidemic periods in geographical regions where cholera is endemic. In the present study, pure cultures of V. cholerae non-O1 cells contained O1 cells when examined by immune-fluorescence microscopy. Laboratory microcosms were used to examine the outgrowth of the O1 cells in cultures of non-O1 V. cholerae. One O1 cell per 10(6) non-O1 cells could be detected by direct fluorescent-monoclonal antibody staining but only after incubation of the non-O1 culture for 48 h. Individual O1 cells were not detected in cultures incubated less than 48 h. Hybridization study, using a polymerase chain reaction (PCR) amplified fragment of the O-antigen of V. cholerae O1 as a probe, revealed the existence of a homologous gene in a microcosm sample of V. cholerae non-O1 containing serogroup-converted cells. The mechanism by which O1 cells can occur in cultures of non-O1 V. cholerae most likely resulted from spontaneous mutation of gene(s) encoding the O-somatic properties and (or) chemical, physical, or biological changes in the environment inducing expression or repression of the controlling gene(s). These findings have important implications for the epidemiology of cholera and the environmental source(s) of toxin producing V. cholerae O1.

Base Sequence↗
PubMed1995

[Biomechanical evaluation of cervical stability with Halifax clamp after bilateral facetectomy].

With nine fresh adult cervical spine specimens (C3-T1), the three-dimensional motions of C4-5 segment were analysed to evaluate the immediate stability following bilateral facetectomy, Halifax clamp and wire fixation. The results showed that the stability with Halifax clamp was greater than that of the intact state in flexion, extension and lateral bending, but the same as in axial rotation. The stability with wire fixation was greater than that in flexion and equal to that in extension, lateral bending and axial rotation. The ROMs with Halifax Clamp were less than those with wire fixation in flexion, extension and lateral bending, but close to in axial rotation.

Adult↗
PubMed1995

Protection of neonatal kittens against feline immunodeficiency virus infection with passive maternal antiviral antibodies.

OBJECTIVE: Maternal antibodies from either vaccinated or feline immunodeficiency virus (FIV)-infected female cats (queens) were evaluated for their ability to protect kittens against homologous FIV infection. DESIGN: Kittens that received different levels of maternal antiviral antibodies from either vaccinated or infected queens were inoculated with homologous FIV at 1 week post-parturition and monitored for FIV infection. Maternal antiviral antibodies in the kittens were also measured and compared to the level of FIV infection. METHODS: Kittens at 1 week post-parturition were inoculated intraperitoneally with five median cat infectious doses of FIVPet. FIV infection was monitored by virus isolation for infectious FIV and by nested polymerase chain reaction for proviral DNA. Virus-neutralizing (VN) antibodies and antibodies to FIV transmembrane peptide and core protein were also monitored throughout the 25 weeks. RESULTS: Neonatal kittens that received high levels of antiviral antibodies from either vaccinated or infected queens were protected from FIV inoculation. Kittens that received low levels of maternal antiviral antibodies were not completely protected from similar FIV inoculation. Protection correlated more closely with the level of maternal VN antibodies than the anti-p25 antibodies transferred to the kittens. The unprotected kittens born to infected queens were not infected from vertical transmission because all littermates that were not FIV-inoculated remained free of FIV infection. CONCLUSIONS: Maternal antiviral antibodies, including VN antibodies, from either vaccinated or infected queens protected neonatal kittens from FIV inoculation. Thus, maternal antiviral antibodies play a key role in preventing or limiting infection in neonates and such antiviral immunity can be provided by vaccinated queens.

Animals↗