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Biomedical subjects

F Xu

Publications and source records attributed to F Xu.

At least 235 records · Page 13Linked to original sources
PubMed1996

Purification, characterization, molecular cloning, and expression of two laccase genes from the white rot basidiomycete Trametes villosa.

Two laccases have been purified to apparent electrophoretic homogeneity from the extracellular medium of a 2,5-xylidine-induced culture of the white rot basidiomycete Trametes villosa (Polyporus pinsitus or Coriolus pinsitus). These proteins are dimeric, consisting of two subunits of 63 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and have typical blue laccase spectral properties. Under nondenaturing conditions, the two purified laccases have different pIs; purified laccase forms 1 and 3 have pIs of 3.5 and 6 to 6.5, respectively. A third purified laccase form 2 has the same N terminus as that of laccase form 3, but its pI is in the range of 5 to 6. The laccases have optimal activity at pH 5 to 5.5 and pH < or = 2.7 with syringaldazine and ABTS [2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid)] as substrates, respectively. The genes lcc1 and lcc2 coding for the two purified laccases (forms 1 and 3) have been cloned, and their nucleotide sequences have been determined. The genes for lcc1 and lcc2 have 8 and 10 introns, respectively. The predicted proteins are 79% identical at the amino acid level. From Northern (RNA) blots containing total RNA from both induced and uninduced cultures, expression of lcc1 is highly induced, while the expression of lcc2 appears to be constitutive. Lcc1 has been expressed in Aspergillus oryzae, and the purified recombinant protein has the same pI, spectral properties, stability, and pH profiles as the purified native protein.

Amino Acid Sequence↗
PubMed1996

Noninvasive determination of cardiac output in patients with severe airflow limitation.

The noninvasive measurement of cardiac output (Q) by the Indirect Fick CO2-rebreathing technique requires mixed venous P CO2 (P CO2) to be determined by the rebreathing maneuver, and Pa CO2 to be estimated from end-tidal P CO2 (PET CO2). Previous work has suggested that although P CO2 can be determined, Pa CO2 cannot be accurately estimated in patients with significant airflow limitation. Nineteen patients with cystic fibrosis who had severe airflow limitation (%FEV1, 29.3 +/- 7.12 SD) were studied during steady-state exercise at 50% of their measured maximal work capacity. Estimated Pa CO2 was slightly lower than Pa CO2 measured from blood samples obtained from an indwelling arterial catheter (measured: 45.2 +/- 4.92; estimate: 42.7 +/- 5.68 mm Hg). To calculate arterial blood content, the values derived from Pa CO2, pH, hemoglobin (Hb), and O2 saturation were compared with those derived from PET CO2 and O2 saturation, where (1) pH was assumed to be 7.40 and Hb was measured, and (2) pH was assumed to be 7.40 and Hb was assumed to be 15 g/dl (measured mean pH, 7.34; Hb, 14.4 g/dl). No difference in arterial CO2 content was seen between the three methods (measured: 47.53 +/- 5.17; estimate 1: 49.57 +/- 6.58; estimate 2: 49.12 +/- 6.61 ml/100 ml). As pH and Hb can also affect mixed venous CO2 content, the effect on Q was also assessed. Both estimates fit closely with measured Q (r2=0.77 and 0.76), with intercepts not different from zero and slopes not different from 1, and coefficients of variation of 13.5 and 14.6%. When viewed with regard to the confidence intervals for Q as a function of O2 consumption, Q was altered to a minor extent. We conclude that the use of PET CO2 to estimate Pa CO2 can give reasonable values for Q determined noninvasively in patients with severe airflow limitation.

Adult↗
PubMed1996

Refractory cytopenia with multilineage dysplasia: further characterization of an 'unclassifiable' myelodysplastic syndrome.

Myelodysplastic syndromes (MDS) characterized by multilineage cytopenias and dysplasia but lacking an increase in blasts, with no Auer rods or monocytosis, do not exactly fit any of the categories of the French-American-British (FAB) classification of MDS and are often diagnosed as refractory anemia (RA), refractory anemia with ringed sideroblasts (RARS), or 'unclassifiable' MDS. It has been suggested that these 'unclassifiable' cases form a distinct subset with a clinical behavior more like that of refractory anemia with excess of blasts (RAEB) than that of RA or RARS, but few studies have been undertaken that characterize this group. We compared the clinical, hematologic, morphologic and cytogenetic features of 18 such patients - for whose disease we propose the designation 'refractory cytopenia with multilineage dysplasia' (RCMD) - to those of 42 patients meeting the FAB criteria for RA or RARS (14 patients) and RAEB (28 patients). Our results show that cytopenias in RCMD are more severe than those in RA or RARS, but are similar to those in RAEB. Erythroid hyperplasia and dyserythropoiesis are the main findings in bone marrow specimens of RA or RARS, but the major features in RCMD are multilineage proliferation and dysplasia, which, except for the lack of increased blasts resemble the findings in RAEB. Only 1/14 patients (7%) with RA or RARS had an abnormal karyotype, whereas RCMD resembled RAEB in terms of the frequency (41 vs 50%, respectively) and type of karyotypic lesions. Abnormalities of chromosomes 5 and 7 (excluding del(5q) as an isolated finding) or complex aberrations were seen only in RCMD and RAEB. in RCMD, the median survival was 24 months, with a 4-year survival rate of48 +/- 13%, intermediate between the findings in RA/RARS (107 months and 77 +/- 12%, respectively) and RAEB (18 months and 27 +/- 9%, respectively). Our data indicate that RCMD is a distinct subset of MDS, with an unfavorable clinical outcome. The designation 'refractory cytopenia with multilineage dysplasia' emphasizes the differences between such cases and the primarily dyserythropoietic, indolent subgroups of MDS, such as RA or RARS.

Adult↗
PubMed1996

Potential of chimaeric plant virus particles as novel, stable vaccines.

Technology has been developed for the expression of multiple copies of epitopes from human and animal pathogens on the surface of assembled particles of a plant virus (cowpea mosaic virus). The technology, termed the Chimaeric Virus Particle (CVP) Technology, can be exploited for the production of vaccines in plants. Each chimaeric virus particle contains 60 copies of the foreign peptide which are expressed in highly exposed positions on the surface of the virus particle. Viral and bacterial epitopes have been expressed as CVPs in an immunologically active form. CPMV is stable at temperatures up to 65 degrees C and a chimaera expressing an HIV epitope survives exposure to a protease and to pH values as low as 1.0.

AIDS Vaccines↗
PubMed1996

[Mechanism of injury of intestine, liver and lung in acute cholangitis of severe type model and the protective effect of huoxue qingjieling].

Lung capillary permeability was measured with 125I labelled bovine serum albumin, the progression of hepato-cellular injury was quantitatively assessed using atriphenyltetrazolium chloride assay, injury of small intestinal mucosa was determined by the changes of diamine oxidase (DAO) level, content of oxygen free radicals (OFR) was measured by electron spin resonance spectrometer and levels of phospholipase A2(PLA2) of intestine, hepatocellular viability were observed by bioassay methods respectively. The results showed that function of lung, liver and intestine was seriously injuried in ACST rats. These injuries demonstrated by increase of capillary permeability and decrease of hepatocellular viability as well as DAO in intestinal mucosa (P < 0.01) in comparing with control, while the levels of OFR and PLA2 in the above-mentioned 3 organs were elevated simultaneously (P < 0.01). As for the comparison of efficacy of different treatment, Huoxue Qingjieling was the best one, the bile duct decompression or ampicillin showed little benefit on injury protection even aggravated in some tissues, they displayed a close relationship with their influence on the OFR and PLA2. Besides, the levels of OFR or PLA2 in various tissues were different from each other, therefore, the serum levels of OFR or PLA2 can not reflect the real levels occurred in organ or tissue level.

Acute Disease↗
PubMed1996

Evaluation of glucose metabolic disorder: insulin resistance and insulin receptors in critically ill children.

OBJECTIVE: To explore the pathogenesis of glucose metabolic disorder and insulin resistance in critically ill children under severe stress. METHODS: To test glucose, lactate, glucagon, insulin, c-peptide, cortisol levels in 50 critically ill children. While we measured 125I-insulin binding to erythrocytes of 13 critically ill children who had hyperglycemia and hyperinsulinemia. Glucose and lactate were measured biochemically. Insulin, c-peptide, cortisol and glucagon were determined by RIA. Erythrocytes insulin receptor was detected by insulin radioreceptor assay. RESULTS: Glucose, lactate, insulin, c-peptide, glucagon, cortisol, insulin/glucose, insulin/glucagon ratio in patients were higher than those in normal controls (P < 0.05). As compared with normal controls, the maximum 125I-insulin bound and insulin receptor number per cell were significantly lower (P < 0.01). But there was no difference of mean value in receptor affinity (P > 0.05). CONCLUSIONS: Hyperglycemia is common in critically ill children during stress, which may be attributed to hormones disturbance and tissure insulin resistance. Insulin receptor defect due to comprehensive factors was one of the important causes for insulin resistance. The blood glucose level can be used as an predicting index in ICU.

Blood Glucose↗
PubMed1996

[Diterpeniod constituents in Rabdosia japonica (Burm.f.) Hara].

Three diterpenoid compounds were isolated from Rabdosia japonica distributed in the easteur past of Anhui Province and identified as trichorabdal H, shikokianin and macrophyllin B on the basis of spectral evidence. They were obtained from this plant for the first time.

Anti-Infective Agents↗
PubMed1995

Medullary respiratory neuronal activity modulated by stimulation of the fastigial nucleus of the cerebellum.

The ability of the rostral fastigial nucleus (FNr) of the cerebellum to modulate medullary respiratory neuronal activity was examined in 17 anesthetized, paralyzed and ventilated cats. A bipolar stimulating electrode was positioned into the FNr and tungsten microelectrodes used to record units within the nucleus tractus solitarius (NTS), nucleus ambiguus (NA) and nucleus retroambigualis (NRA). Transient stimuli (< 150 microA, 5-200 Hz) were delivered during inspiration or expiration, and the effects noted on medullary neuronal activity and the phrenic neurogram. The results showed that FNr stimulation: (1) modulated inspiratory and expiratory neuronal (ramp-, early- and late-inspiratory and stage I and II expiratory) discharges recorded from the NTS, NA and NRA (n = 67, 14 and 28) when stimuli (> or = 20-50 Hz) were delivered during either the inspiratory or expiratory phases; (2) terminated the burst durations of inspiratory (77%) and expiratory (94%) neurons with stimulus-response latencies of 28.2 +/- 3.1 ms (inspiratory) and 29.4 +/- 3.6 ms (expiratory); (3) elicited changes in phrenic neurogram concomitant with the effects noted on medullary neuronal activities; (4) failed to change heart rate and arterial blood pressure; and (5) did not affect medullary neuronal and phrenic nerve activity following kainic acid injection into the FNr. We conclude that activation of the FNr (likely its cell bodies) can modulate the respiratory output via influences on medullary respiratory-related neurons. The primary cerebellar effect across all sub-types of respiratory neurons was early termination.

Anesthetics, Intravenous↗
PubMed1995

RNA degradation in Escherichia coli regulated by 3' adenylation and 5' phosphorylation.

Although polyadenylation has commonly been regarded as a special feature of eukaryotic messenger RNA, there are many reports of polyA tails on bacterial RNA (for example, refs 3-8). In Escherichia coli, adenylation mediated by the pcnB gene greatly accelerates decay of RNA I, an antisense repressor of replication of ColE1 type plasmids that resembles highly structured transfer RNA but shows the rapid turnover characteristic of mRNA. Here we report that both 3' adenylation and 5' phosphorylation affect the rate of digestion of RNA I by the 3' exonuclease, polynucleotide phosphorylase; conversely, mutation of the polynucleotide phosphorylase-encoding pnp gene affects ribonuclease acting at the 5' end. Together these findings indicate that enzymes attacking RNA I at its separate termini can interact functionally. Additionally, our discovery that adenylation-mediated degradation by polynucleotide phosphorylase imparts an mRNA-like half-like to RNA I suggests a possible mechanism to account for the rapid decay of mRNA in E. coli.

Adenine↗
PubMed1995

Combinations of multiple serum markers are superior to individual assays for discriminating malignant from benign pelvic masses.

To determine whether measurement of the levels of multiple tumor markers in the preoperative serum of women presenting with a pelvic mass distinguished benign from malignant disease better than the assay of CA 125 alone, sera from 429 patients, 192 of whom had malignant histology, were assayed for 8 different markers: CA 125, macrophage colony-stimulating factor, OVX1, lipid-associated sialic acid (LASA), CA15-3, CA72-4, CA19-9, and CA54/61. The sensitivity and specificity of CA 125 alone (> 35 U/ml) was 78.1 and 76.8%, respectively. A panel consisting of CA 125, OVX1, LASA, CA15-3, and CA72-4 had a sensitivity of 83.3% and specificity of 84.0% when two or more markers were elevated. Using the concentrations of these five markers, logistic regression analysis had a sensitivity of 85.4% and a specificity of 83.1%. Considering the values of markers in different sequences, classification and regression tree analysis substantially improved the sensitivity to 90.6% and the specificity to 93.2%. When applied in clinical practice this approach could improve the management of women presenting with a pelvic mass and may also have application in screening for ovarian cancer.

Biomarkers, Tumor↗
PubMed1995

Weird past tense forms.

It is often assumed that children go through a stage in which they systematically overapply irregular past tense patterns to inappropriate verbs, as in wipe-wope, bring-brang, trick-truck, walk-has walken. Such errors have been interpreted both as reflecting over-use of minor grammatical rules (e.g. 'change i to a'), and as reflecting the operation of a connectionist pattern associator network that superimposes and blends patterns of various degrees of generality. But the actual rate, time course, and nature of these errors have never been documented. We analysed 20,000 past tense and participle usages from nine children in the CHILDES database, looking for overapplications of irregular vowel-change patterns, as in brang, blends, as in branged, productive suffixations of -en, as in walken, gross distortions, as in mail-membled, and double-suffixation, as in walkeded. These errors were collectively quite rare; children made them in about two tenths of one per cent of the opportunities, and with few stable patterns: the errors were not predominantly word-substitutions, did not occur predominantly with irregular stems, showed no consistency across verbs or ages, and showed no clear age trend. Most (though not all) of the errors were based closely on existing irregular verbs; gross distortions never occurred. We suggest that both rule-theories and connectionist theories have tended to overestimate the predominance of such errors. Children master irregular forms quite accurately, presumably because irregular forms are just a special case of the arbitrary sound-meaning pairings that define words, and because children are good at learning words.

Child↗
PubMed1995

Effect of prolonged exercise at 65 and 80% of VO2max on running economy.

The purpose of this study was to investigate the effect of prolonged exercise at 65 and 80% of VO2max on running economy. Fourteen male long distance runners performed two 90-min runs on an outdoor 400 m track at velocities of 65 and 80% of VO2max. Prior to and following each 90-min run, running economy was measured as the steady-state VO2 during treadmill runs at speeds of 188 and 228 m/min. During the 90-min run at 65% of VO2max, the mean weight loss was 1.3 kg. HR increased from 143 bpm between minutes 5-10 to 150 bpm between minutes 85-90. During the 90-min run at 80% of VO2max, the mean weight loss was 1.4 kg. The HR was 161 bpm between minutes 5-10 and increased to 165 bpm between minutes 85-90. When the post running economy test was conducted following each 90-min run, there was a significant increase in VO2 expressed in both l/min and ml/kg min. The increase in VO2 following the 90-min run at 80% of VO2max. These results suggest that 90-min runs at 65 and 80% of VO2max alter running economy with a significant increase in oxygen cost.

Adult↗
PubMed1995

Expression of a murine cytomegalovirus early-late protein in "latently" infected mice.

Monoclonal antibodies were isolated from the spleen of a latently infected mouse to identify possible antigenic markers for latent murine cytomegalovirus infection. One antibody, AM3, was selected for further study. Characterization of the antigen recognized by AM3 confirmed that it is the early-late phosphoprotein pp50. The antigen was readily detected by immunoautoradiography in the spleens of acutely and latently infected mice. Low levels of the AM3/pp50 transcript were also detected in latently infected tissues by in situ hybridization. Presence of AM3/pp50 mRNA, as well as IE-1 transcripts, was confirmed by reverse transcription-polymerase chain reaction in 3 of 5 latently infected spleens. The expression of both immediate-early and early-late classes of viral genes suggests that persistent infection may be a component of the MCMV life cycle operationally defined as latency and that this gene is not specific for latency.

Animals↗