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Biomedical subjects

L F Zhang

Publications and source records attributed to L F Zhang.

At least 91 records · Page 5Linked to original sources
PubMed1994

Exposure of bus and taxi drivers to urban air pollutants as measured by DNA and protein adducts.

Urinary 1-hydroxypyrene, lymphocyte DNA adducts, serum protein-bound PAH and hemoglobin-bound alkene adducts were analysed from 4 groups of non-smoking men: urban and suburban bus drivers, taxi drivers and suburban controls. The only differences between the groups were in DNA adducts between suburban bus drivers and controls, and in DNA adduct and plasma protein PAH-adducts between taxi drivers and controls.

Air Pollutants↗
PubMed1994

p53 mutations in larynx cancer.

The objective of this work was an analysis of mutations in the p53 gene detected from fresh tumor samples of larynx cancer patients using single-strand conformation polymorphism (SSCP) and direct DNA sequencing of exons 5-8. From 40 patient samples, 15 showed an extra band in SSCP. In 13 samples mutations were detected in exons 5-8. They constituted six transitions and seven transversions, four of them being T to A transversions. Mutations in codons 205 and 248 occurred in two and in codon 246 in three samples. Larynx cancer is strongly associated with tobacco smoking and alcohol consumption. The typical p53 mutations in lung cancer, G to T transversions and G to A and C to T transitions, associated with smoking, accounted for 46% of the mutations detected. Fifty-four per cent of the mutations were detected in a reported hotspot region covering codons 238-248.

Adult↗
PubMed1994

[Quantitative study on DNA-adduct in normal lung tissues of smoking and non-smoking lung cancer patients].

Lung tissues from 32 cases of lung cancer with surgical operation, 22 smokers and 10 nonsmokers, were analyzed with P1-mediated modification of 32P-postlabelling technique. The level of lung DNA-adduct in cigarette smokers was higher that in nonsmokers with significant difference (P < 0.001). Autoradiogram showed a diagonal radioactive zone in smokers' lung tissues. Correlation analysis indicated DNA-adduct in lung tissues increased with the number of cigarettes smoked with a regression equation of Y = 0.411 X + 3.52, r = 0.74, P < 0.001.

Adult↗
PubMed1994

[Histopathological findings of 59 cases of cheilitis granulomatosa].

By histopathological observations of 59 cases of CG, they are divided into 6 types according to pathological characteristics. Their differences are compared and discussed. The reason and significance of this classification from morphological point of view are discussed as well. It is suggested that the G is possibly resulted from different reactions of the body to the same pathogen or to the different pathogens.

Humans↗
PubMed1994

Immunohistochemical study of hepatitis E virus antigen in liver tissues from patients with hepatitis E.

Hepatitis E virus antigen (HEVAg) has been identified in liver tissue of 6 out of 14 patients with hepatitis E using anti-HEV-IgG-horseradish peroxidase (HRP) and direct immunoperoxidase staining methods. HEVAg was found only in the cytoplasm of hepatocytes, but nor in the nuclei. The HEVAg positive hepatocytes were scattered singly, but in a few parts, where the liver damage was severe, the HEVAg positive cells were quite concentrated. We also observed the invasion of lymphocytes into the HEVAg positive hepatocytes. These phenomena suggest that the liver damage may be related to the immune reaction. No HEVAg was found in the liver tissues of stillborn fetus and neonate from woman patients with hepatitis E.

Adult↗
PubMed1993

Cardiovascular deconditioning effects of long-term simulated weightlessness in rats.

The aim of our serial work was to investigate the cardiovascular deconditioning effect of long-term simulated weightlessness and to elucidate its mechanisms. Our research goal was established in view of the following three reasons. Firstly, even after several decades of extensive research, there still exist significant gaps in our knowledge concerning microgravity induced cardiovascular effect. Secondly, to guarantee the health and safety of astronauts in the future prolonged missions, it is important to understand the cardiovascular adaptation to long-term weightlessness. Thirdly, the reported ultrastructural degenerative changes in myocardium of rats flown on the Cosmos 1887 biosatellite has raised concerns about the question whether long-term spaceflight may lead to myocardial degeneration. To achieve this, we considered an appropriate animal model to simulate cardiovascular and other effects of long-term microgravity was of first importance. By making some modifications to the Morey-Holton's model, a method of long-term tail-suspension with less stressful influence and no injurious effects on the tail skin was developed. Up to now, the longest period of suspension in our laboratory has been of 120-day long. In this paper, we will focus primarily on the findings from our recent works on the cardiovascular deconditioning effect of 90-/120-day tail-suspension and changes in baroreflex responsiveness and in contractility and ultrastructure of the heart in rats.

Animals↗
PubMed1992

Estimation of respiratory mechanics in dogs with acute lung injury.

In mechanically ventilated anesthetized dogs with acute lung injury induced by intravenous infusion of oleic acid (OA), changes in airflow, lung volume, and tracheal (Pao), transpulmonary (Ptp) pressures were measured. Changes in lung mechanics were studied before and after OA infusion at intervals, during an observation period lasting 4-5 hours, by using the interrupter technique and identification technique, and by measuring the pressure-volume (PV) characteristics. The main results are listed as follows: (1) compliance and FRC showed a marked decrease, Pao and Ptp showed a marked increase within 2 hours after OA. (2) airflow resistance estimated by the identification technique showed a marked increase after OA. (3) static PV characteristics of both the lungs and total respiratory system showed similar changes 4 hours after OA, characterized by the presence of an inflexion on the inflation limb, increased hysteresis and a rightward and downward shift of the loop. (4) the trend of changes of dynamic PV characteristics obtained by changing the PEEP value in a stepwise manner, with the ventilation uninterrupted, was similar to that of the static PV curve. It is suggested that an on-line identification technique with one-compartment model to track the slow changes in combination with serial measurements of the dynamic PV characteristics of the total respiratory system would be more appropriate for monitoring lung mechanics of ventilated patients with ARDS.

Animals↗
PubMed1992

[Immunohistochemical study of hepatitis E virus antigen in liver tissues from patients with type E hepatitis].

Hepatitis E virus antigen (HEV Ag) has been identified in liver tissues of 6 out of 14 patients with type E hepatitis by direct immunoperoxidase staining, using anti-HEV-IgG-HRP. HEV Ag was found to be diffusive or inclusive in the cytoplasm of hepatocytes were scattered and isolated, but might aggregate in some parts where the liver damage was severe. We found that lymphocyte invaded the HEV Ag positive hepatocyte. These phenomena suggest that the liver damage is related to immunoreaction. HEV Ag was not found in the liver tissues of stillborn fetus and newborn baby from woman patients with hepatitis E. To detect HEV Ag in liver with direct immunoperoxidase method, using anti-HEV-IgG-HRP is more efficient than using anti-HEV-IgM-HRP.

Antigens, Viral↗
PubMed1991

Cloning and expression of penicillin G acylase gene in Bacillus megaterium.

Bacillus megaterium BM1, which produces penicillin G acylase (PGA), has been isolated. Gene encoding for PGA was cloned into E. coli MC1061 using pBR322 as the vector, obtaining a recombinant plasmid pBmPA4 containing 9.9 kb inserted DNA. Restriction map of the plasmid was analyzed. A pBmPA5 containing 4.9 kb was gained by deletion in vitro. Both pBmPA4 and pBmPA5 clones can be expressed in E.coli MC1061, and their expressions were induced by phenylacetic acid.

Bacillus megaterium↗
PubMed1989

The effect of IABP ventricular contractility of the normal and ischemic canine heart assessed in situ by T-Emax.

The effects of IABP on the contractile state of the in situ canine heart was evaluated under control conditions and conditions of regional ischemia by determining the transient slope of the end-systolic pressure-volume line, T-Emax. For comparison, the conventional index reflecting contractility, dP/dtmax and other related hemodynamic parameters were also assessed. The results showed that, T-Emax, rather than dP/dtmax, reflected more appropriately the changes in contractile state during activation of the IABP under both conditions. It suggests that IABP has a positive inotropic influence only in the ischemic-state and this is a positive inotropic influence only in the ischemic-state and this is a result of the improvement in the myocardial oxygen supply and demand relation. In addition, the limitations of the new indicator, T-Emax, is discussed.

Animals↗
PubMed1988

Effects of combined resistive loading on the respiratory pattern and the subject's perception.

The physiological and psychophysical effects of combined flow resistive loads were studied systematically by using the Multistage Evaluation Scale (MES), determining the number of Just Noticeable Difference (JND) steps, and constructing equivalent resistive-load-sensation contours. During combined resistive loading, the relative changes of inspiratory and expiratory peak flow rate (VImax/VEmax) were related to both the JND step number and the inspiratory versus expiratory resistance ratio (IR/ER). However, the ratio VImax/VEmax was related to the IR'/ER' ratio only. The subject's perception of combined loads differing both in intensity and IR/ER ratio could be well depicted by the equivalent resistive-load-sensation contours. Hence we could define a model for predicting the physiological and psychophysical effects of various resistive loading conditions.

Humans↗
PubMed1988

Multistage evaluation scale, differential threshold steps and equivalent sensation contours of respiratory flow-resistive load sensation.

This paper presents and discusses the methodology and results of studies on respiratory sensation by using a fuzzy set category judgement model and applying the concept of just noticeable difference (JND) step and equivalent sensation. A new kind of category scale, the multistage evaluation scale (MES), based on a fuzzy set category judgement model for quantifying respiratory sensory magnitude has been put forward and verified in 37 subjects. The perceived magnitude of added resistance estimated using MES could reflect properly the difference in sensory perception caused by added loads with equal intensity but applied to different phases of the breathing cycle. In addition, the psychophysical function obtained conforms to the Stevens' power law. On the contrary, the classical category scale does not possess some of these attributes. In 9 subjects, we determined that the sensory continuum corresponding to either inspiratory or expiratory added resistive load, ranging 10-500 mm H2O.1(-1).s, consisted of 6 or 7 JND steps. The sensory magnitude corresponding to each step was estimated by the MES. Relating the results of JND step measurements with that of magnitude estimation using MES, we could elucidate systematically the relationship between perceived magnitude and discrimination for respiratory sensation. In 13 subjects, the equivalent respiratory resistive load sensation contours of 2, 3 and 4 JND step above basal level, respectively, were obtained through experimentation and by quadratic polynomial approximation of experimental data. The results suggest that as regards the human tolerance to various added resistive loads the combined resistive load is the most tolerable among the three; the expiratory, the least. The equivalent sensation contour can be used to predict the changes in respiratory sensation determined by both the intensity of the total added load and the ratio of inspiratory versus expiratory load. In brief, we have proposed a new way to elucidate the physiological and psychophysical effects of various added resistive loads.

Humans↗
PubMed1986

A method for screening penicillin G acylase-producing bacteria by means of 2-nitro-5-phenylacetaminobenzoic acid test paper.

A simple, rapid assay for screening penicillin G acylase-producing bacteria is presented. The method is based on the formation of yellow 2-nitro-5-aminobenzoic acid by penicillin G acylase acting on 2-nitro-5-phenylacetaminobenzoic acid (NIPAB). NIPAB test paper is briefly applied to bacterial colonies on the agar surface, which are subsequently scored individually on the paper by color; bright yellow indicates the presence of penicillin G acylase, natural color its absence. The present method is suitable not only for screening penicillin G acylase-production by a variety of bacteria but also for detection from a large number of transformant colonies of clones containing a gene encoding for the enzyme.

Amidohydrolases↗
PubMed1983

Direct determination of phenylalanine in serum extracts of phenylketonuria patients by reversed-phase high-performance liquid chromatography.

A method for direct determination of phenylalanine (Phe) in serum extract by reversed-phase high-performance liquid chromatography with an octadecylsilane column has been devised. Phe is monitored at 220 nm with a UV detector. The mobile phase is a mixture of methanol and water (10:90) with added phosphoric acid and potassium dihydrogen phosphate and has a pH value of 4.3. The minimum detectable amount is 6 ng. The average contents of Phe found for healthy adults and children are 12 and 15 micrograms/ml respectively. Phe contents of sera of three phenylketonuria children are about 10 to 15 times higher than these values.

Adult↗