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Biomedical subjects

Z Guo

Publications and source records attributed to Z Guo.

At least 397 records · Page 22Linked to original sources
PubMed1995

[Escharectomy during burn shock stage contributed to controlling or alleviating infectious complication].

Among 29 patients with extensive burn, 14 received escharectomy during the shock period, and the other 15 after 96 hrs. LPS and TNF were determined before and after escharectomy 3, 7, 14 and 21 PBD. Incidence of sepsis and subeschar bacterial count were analyzed. Clinical conditions were compared. The results showed that escharectomy during burn shock stage significantly reduced infectious complications in extensively burned patients. We believe that as long as general condition of the patient allowed, early removal of eschar was beneficial in reducing the threat of sepsis.

Adult↗
PubMed1995

[The use of measuring serum soluble IL-2 receptor levels in cyclosporine-A treated lupus nephritis].

Twenty-one patients with Lupus Nephritis (LN) were treated with cyclosporine-A (CsA) for three months. Serum soluble interleukin-2 receptors (SIL-2R) were measured before and after treatment and correlated prospectively with serologic findings of LN activity. The patients had significantly higher IL-2R level before treatment (during LN flare) than after treatment (disease remission). A significant positive correlation was present between serum SIL-2R and proteinuria, and ANA as well, whereas the SIL-2R levels in LN patients were inversely correlated with serum levels of C3 and CH50. These observations suggest that serum SIL-2R level is an useful marker of disease activity in LN and may serve as a helpful adjunct in the management of this disorder.

Adult↗
PubMed1995

[Assessment of effectiveness of AgSD-ZnSD-Azone cream, negative ion irradiation and "moisture burn ointment" in prevention of burn wound infection as judged by changes in LPS, TNF and ET levels].

40 Wistar rats were scalded resulting in 15% TBSA full-thickness burn. Pseudomonas aeruginosa (10(9)/ml) was seeded on the wounds. The animals were divided into 4 groups. AgSD and ZnSD (with Azone) cream was applied to the wounds in the group I. The wounds were irradiated with negative ion current in the group II. The "moisture burn ointment" was applied to the wounds in the group III. Group IV consisted of controls without any treatment. Judging by changes in levels of LPS, TNF and ET, it was shown that the best result was obtained in the group I and II. The "moisture burn ointment" group yielded the poorest results.

Animals↗
PubMed1995

[Chemical constituents of Euphorbia hylonoma Hand. -Mazz].

Three compounds have been isolated from the root of Euphorbia hylonoma and identified as 3,3',4-tri-O- methylellagic acid, beta-sitosterol and sucrose by physicochemical and spectroscopic methods. The compound 3,3'4-tri-O-methylellagic acid is discovered in Euphorbia for the first time.

Drugs, Chinese Herbal↗
PubMed1995

[The effect of different topical agents on pseudomonas infection of burn wound].

48 Wistar rats were scalded resulting in 15% TBSA full-thickness burn. Pseudomonas aeruginosa (10(9)/ml was inoculated to the wounds. The rats were divided into 6 groups. 5 different topical agents were separately applied to the wounds constituting 5 groups, and no drug was used in control group. Through observing the appearance of wound, the quantity of bacteria in the subeschar tissue and histo-pathological changes, we confirmed that AgSD-ZnSD-A cream was a satisfactory topical agent.

Animals↗
PubMed1995

[The characteristics of inhalation injury and pulmonary infection in burn patients and the influence on their mortality].

940 patients with thermal injury during the past 14 years were reviewed. Of them, inhalation injury was diagnosed in 75 patients, including 15 mild injury who all survived, 25 moderate injury, of whom 13 died with a mortality rate of 52.0% and 35 severe injury, of whom 31 died with a mortality rate of 88.6%. The data showed that 70% of burn that caused inhalation injury occurred in a closed space and 96% of which also caused facial injury. With the burn extent increasing, the incidence of inhalation injury and pulmonary infection rise correspondingly. The time and incidence of pulmonary infection in the patients with inhalation injury was earlier and higher than that in those without inhalation injury (P < 0.01). With similar burn area and age, the risk of death in the patients with inhalation injury was 17.2 times of the patients without inhalation injury (P < 0.001). Pulmonary infection further increased mortality of the patients (P < 0.001).

Adolescent↗
PubMed1994

Direct fluorescence analysis of genetic polymorphisms by hybridization with oligonucleotide arrays on glass supports.

A simple and rapid method for the analysis of genetic polymorphisms has been developed using allele-specific oligonucleotide arrays bound to glass supports. Allele-specific oligonucleotides are covalently immobilized on glass slides in arrays of 3 mm spots. Genomic DNA is amplified by PCR using one fluorescently tagged primer oligonucleotide and one biotinylated primer oligonucleotide. The two complementary DNA strands are separated, the fluorescently tagged strand is hybridized to the support-bound oligonucleotide array, and the hybridization pattern is detected by fluorescence scanning. Multiple polymorphisms present in the PCR product may be detected in parallel. The effect of spacer length, surface density and hybridization conditions were evaluated, as was the relative efficacy of hybridization with single or double-stranded PCR products. The utility of the method was demonstrated in the parallel analysis of 5 point mutations from exon 4 of the human tyrosinase gene.

Alleles↗
PubMed1994

Expression of modified human cytochrome P450 1A1 in Escherichia coli: effects of 5' substitution, stabilization, purification, spectral characterization, and catalytic properties.

Human cytochrome P450 (P450) 1A1 is primarily an extrahepatic enzyme and is important because of its roles in the activation of polycyclic hydrocarbons and other xenobiotic chemicals. Purification of active enzyme from human tissues has not been successful. We report the expression and purification of the recombinant enzyme from Escherichia coli. A full-length cDNA of human cytochrome P450 1A1 and several modified constructs were engineered into a pCW vector and used to transform E. coli cells. Little expression was observed with the native sequence and several modified constructs, but successful expression (20-25 nmol membrane-bound P450 1A1 per liter of culture) was achieved with a construct in which the Ala codon GCT was placed in the second position and the 5'-terminal codons were maximized for AT content and minimized for the potential of secondary structure formation of the mRNA transcript. alpha-Naphthoflavone was found to protect against denaturation by detergents during solubilization and was added to buffers used for purification. The recombinant P450 1A1 was purified to electrophoretic homogeneity after two ion-exchange chromatography steps in approximately 50% yield. N-Terminal amino acid sequence analysis verified the expected first 21 residues, with the exception of the terminal Met. The isolated human ferric P450 1A1 was predominantly in the high spin state, in contrast to the orthologous rat and rabbit enzymes. Recombinant P450 1A1 catalyzed 7-ethoxyresorufin O-deethylation and benzo[a]pyrene 3-hydroxylation with Km values of 0.58 and 15 microM and Vmax values of 8.3 and 2.5 nmol min-1 (nmol P450 1A1)-1, respectively. The successful expression and purification of human P450 1A1 should increase the availability of this enzyme and the generation of antibodies for further biochemical and other biological studies.

Amino Acid Sequence↗
PubMed1994

Expression of modified human cytochrome P450 1A2 in Escherichia coli: stabilization, purification, spectral characterization, and catalytic activities of the enzyme.

A full-length human cytochrome P450 (P450) 1A2 cDNA clone and four derivatives in which the 5'-terminus was modified were inserted into the pCW vector and used to transform Escherichia coli cells. Low levels of expression were seen with most of the constructs but high expression levels (245 nmol membrane-bound P450 recovered per liter culture) were achieved when the N-terminus was MALLLAVFL, as reported earlier by Fisher et al. (C. W. Fisher, D. L. Caudle, C. Martin-Wixtrom, L. C. Quattrochi, R. H. Tukey, M. R. Waterman, and R. W. Estabrook, 1992, FASEB J. 6, 759-764). The expressed human P450 1A2 in bacterial membranes was rapidly denatured to cytochrome P420 in the presence of detergents. This denaturation was blocked by the inhibitory ligand alpha-naphthoflavone (alpha NF, 7,8-benzoflavone). Human P450 1A2 was solubilized using high concentrations of sodium cholate and Triton N-101 and could be purified to near homogeneity in high yield in two steps. alpha NF was included in the buffer in the first step and then removed in the second chromatography step along with the detergent. The purified human P450 1A2 was found to be almost completely in the high spin iron configuration, in contrast to P450 1A2 enzymes isolated from rats and rabbits. The enzyme was catalytically active toward the known substrates 7-ethoxyresorufin and phenacetin. The N-terminal appears to be blocked, as is the case for other P450s we have expressed that contain the sequence MALLLAVFL in E. coli. Previously this human P450 has only been available in limited amounts; the methods presented here should facilitate further biochemical and practical studies on this interesting enzyme.

Amino Acid Sequence↗
PubMed1994

Biosynthesis of the diterpene cis-abienol in cell-free extracts of tobacco trichomes.

Biosynthesis of the hydroxylated labdane diterpene, cis-abienol, 9 alpha H-[(12Z)-labda-12,14-dien-8 alpha-ol] from geranylgeranyl pyrophosphate was observed in cell-free extracts prepared from trichome-bearing tissues of the experimental tobacco, Nicotiana tabacum L. c.v. T.I. 1068. Synthetic activity was observed with extracts of trichome glands, but not subepidermal tissue or epidermis from which glands had been removed. The activity was soluble, Mg2+ stimulated, had a pH optimum near 7.0, and was unaffected by conditions which inhibit cytochrome P450 oxygenase. These results indicate the occurrence in trichome glands of T.I. 1068, a cyclase activity which yields the cyclized hydroxylated labdanoid cis-abienol directly.

Cell-Free System↗
PubMed1994

Expression of modified human cytochrome P450 2E1 in Escherichia coli, purification, and spectral and catalytic properties.

Human cytochrome P450 (P450) 2E1 is of interest because of its role in the oxidation of numerous drugs and carcinogens. The purification of the protein from human liver is difficult, and we report the development of a system for relatively high-level expression in Escherichia coli. A cDNA was prepared from liver cDNA by polymerase chain reaction methods and several variants with modified 5'-termini were constructed. Analysis of seven of these indicated that the highest levels of expression were found when the first 21 codons of the native sequence were deleted and the Trp immediately following the resulting N-terminal Met was changed to Ala (GCT). Levels of 40-nmol membrane-bound P450 2E1 (liter culture)-1 were routinely recovered. The recombinant P450 2E1 was purified to electrophoretic homogeneity from the bacterial membranes in two ion-exchange steps in > 80% yield. Ferric P450 2E1 was isolated in a mixed spin state. The enzyme was active in chlorzoxazone 6-hydroxylation; the addition of human liver cytochrome b5 lowered the Km for the substrate and increased Vmax. N-Terminal amino acid sequence analysis yielded the expected first 21 residues. The expression system should facilitate the availability of human P450 2E1 and antibodies for studies of the enzyme.

Base Sequence↗
PubMed1994

Artificial neural networks in computer-assisted classification of heart sounds in patients with porcine bioprosthetic valves.

The paper describes the design, training and testing of a three-layer feed-forward back-propagation neural network for the classification of bioprosthetic valve closure sounds. Forty-seven patients with a porcine bioprosthetic valve inserted in the aortic position were involved in the study. Twenty-four of them had a normal bioprosthetic valve, and the other 23 had a degenerated valve. Five features extracted from the Fourier spectra and 12 linear predictive coding (LPC) coefficients of the sounds were used separately as the input of two neural-network classifiers. The performance of the classifiers was tested using the leave-one-out method. Results show that correct classifications were 85 per cent using the spectral features, and 89 per cent using the LPC coefficients. The study confirms the potential of artificial networks for the classification of bioprosthetic valve closure sounds. Clinical use of this method, however, still requires further investigation.

Aortic Valve↗
PubMed1994

Classification of lower limb arterial stenoses from Doppler blood flow signal analysis with time-frequency representation and pattern recognition techniques.

A pattern recognition system was used to classify Doppler blood flow signals for the determination of lower limb arterial stenoses. The diagnostic features were extracted from time-frequency representations of Doppler signals. Three techniques were tested to estimate time-frequency representations: the short-time Fourier transform, the autoregressive (AR) modeling, and the Bessel distribution. A boundary tracking algorithm was proposed to extract the frequency contour of the Doppler time-frequency representations. Based on the characteristics of the Doppler frequency contour, shape descriptors from an autoregressive analysis were proposed as diagnostic features. Simple algorithms were proposed to normalize these autoregressive shape descriptors. Amplitude distribution of the Doppler time-frequency representation was also found useful for stenosis classification. A total of 379 arterial segments from the aorta to the popliteal artery were classified by the pattern recognition system into three categories of diameter reduction (0-19%, 20-49%, and 50-99%). The short-time Fourier transform provided an overall accuracy of 80% (kappa = 0.38); AR modeling, 81% (kappa = 0.42); and the Bessel distribution, 82% (kappa = 0.43). All these results are better than those based on visual interpretation (accuracy = 76%, kappa = 0.29) performed by a trained technologist. The AR modeling and the Bessel distribution improved the performance of the pattern recognition system in comparison with the short-time Fourier transform. It is likely that with further improvement, the pattern recognition approach will be a useful clinical tool to quantify stenoses and to follow the disease progression with more reliability and less bias than visual interpretation as done currently in clinical practice.

Adult↗
PubMed1994

Activation of procarcinogens by human cytochrome P450 enzymes expressed in Escherichia coli. Simplified bacterial systems for genotoxicity assays.

Bacterial assays were used to examine the activation of 14 known procarcinogens by cytochrome P450 (P450) enzymes. Human P450s 1A1, 1A2 and 3A4 were expressed in Escherichia coli with slight modification of their N-terminal sequences. Genotoxicity was measured by the induction of the SOS response in Salmonella typhimurium NM2009 (TA1535/pSK1002/pNM12), which contains a umuC regulatory sequence attached to the lacZ reporter gene. Conditions for analysis were examined using E. coli membranes and purified enzymes. Membrane fractions, fortified with NADPH-P450 reductase, were found to be useful preparations for measuring activation of the procarcinogens. Conditions of linearity were established for these assays and the systems were applied to several particular problems related to bioactivation of procarcinogens by P450s. The patterns of activation of the 14 individual chemicals were consistent with the literature developed using human liver microsomes, purified liver P450s and other approaches. The P450s expressed in bacterial membranes could be inhibited by antibodies. 7,8-Benzoflavone inhibited P450s 1A1 and 1A2 and stimulated P450 3A4 in the membranes. The contributions of P450s 1A1 and 1A2 were distinguished with some of the arylamines and 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene. Recombinant P450 3A4 was found to be more active than P450 1A2 in the activation of aflatoxin B1 at all substrate concentrations examined.

Amino Acid Sequence↗
PubMed1994

Comparison of time-frequency distribution techniques for analysis of simulated Doppler ultrasound signals of the femoral artery.

The time-frequency distribution of the Doppler ultrasound blood flow signal is normally computed by using the short-time Fourier transform or autoregressive modeling. These two techniques require stationarity of the signal during a finite interval. This requirement imposes some limitations on the distribution estimate. In the present study, three new techniques for nonstationary signal analysis (the Choi-Williams distribution, a reduced interference distribution, and the Bessel distribution) were tested to determine their advantages and limitations for analysis of the Doppler blood flow signal of the femoral artery. For the purpose of comparison, a model stimulating the quadrature Doppler signal was developed, and the parameters of each technique were optimized based on the theoretical distribution. Distributions computed using these new techniques were assessed and compared with those computed using the short-time Fourier transform and autoregressive modeling. Three indexes, the correlation coefficient, the integrated squared error, and the normalized root-mean-squared error of the mean frequency waveform, were used to evaluate the performance of each technique. The results showed that the Bessel distribution performed the best, but the Choi-Williams distribution and autoregressive modeling are also techniques which can generate good time-frequency distributions of Doppler signals.

Bias↗
PubMed1994

Measurement of fractional lipid synthesis using deuterated water (2H2O) and mass isotopomer analysis.

Fractional biosynthesis of palmitate, stearate, and cholesterol was determined with deuterated water (2H2O) using mass isotopomer analysis in Hep G2 and MCA sarcoma cells in culture. The method employed differs from previous ones in that the number of deuterium atoms from 2H2O incorporated into newly synthesized molecules was determined and not assumed. After correction for background natural abundances, the isotopomer distribution due to deuterium incorporation in fatty acids and cholesterol was shown to follow a simple binomial distribution depending on the deuterium enrichment in water (p) and the maximum number of deuterium atoms incorporated per molecule (N). Under a wide range of 2H2O enrichments, N could be determined to be 17 for palmitate, 20 for stearate, and 20 for cholesterol by regression analysis or from a series of consecutive mass isotopomer ratios. The fraction derived from de novo synthesis was given by the ratio of the observed to the theoretical deuterium enrichment, which is the product (N x p). The new synthesized fraction of palmitate and stearate by Hep G2 cells for the length of the experiment was found to be 77 and 65%, respectively. These values were confirmed by experiments with [U-13C]glucose as the precursor. In MCA sarcoma cells grown in lipid-poor medium, the average values for fractional synthesis of palmitate, stearate, and cholesterol were 70, 35, and 70%, respectively. This approach should be generally applicable to the simultaneous determined of fractional synthesis of a number of compounds with either deuterium or 13C tracers. Its application is only limited by the accuracy of mass spectrometric analysis.

Animals↗