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Z Guo

Publications and source records attributed to Z Guo.

At least 379 records · Page 21Linked to original sources
PubMed1995

Redundant 3' end-forming signals for the yeast CYC1 mRNA.

The cyc1-512 mutation is a 38-bp deletion in the 3' untranslated region of the CYC1 gene, which encodes iso-1-cytochrome c in Saccharomyces cerevisiae. This deletion caused a 90% reduction in the levels of the CYC1 mRNA and protein because of the absence of the normal 3' end-forming signal. Although the 3' end-forming signal was not defined by previous analyses, we report that concomitant alteration by base-pair substitution of three 3' end-forming signals within and adjacent to the 38-bp region produced the same phenotype as the cyc1-512 mutation. Furthermore, these signals appear to be related to the previously identified 3' end-forming signal TATATA. A computer analysis revealed that TATATA and related sequences were present in the majority of 3' untranslated regions of yeast genes. Although TATATA may be the strongest and most frequently used signal in yeast genes, the CYC1+ gene concomitantly employed the weaker signals TT-TATA, TATGTT, and TATTTA, resulting in a strong signal.

Base Sequence↗
PubMed1995

Expression of cytochrome P450 3A5 in Escherichia coli: effects of 5' modification, purification, spectral characterization, reconstitution conditions, and catalytic activities.

Cytochrome P450 (P450) 3A5 is a human enzyme with 85% amino acid sequence identity to the more predominantly expressed P450 3A4 and has been reported to have overlapping catalytic specificity. The 5'-terminus of a P450 3A5 cDNA was modified for optimal expression in Escherichia coli using the vector pCW, by aligning the MALLLAVFL N-terminal sequence of recombinant bovine P450 17A (H. J. Barnes, M. P. Arlotto, and M. R. Waterman, (1991) Proc. Natl. Acad. Sci. USA 88, 5597-5601) to the 3A5 cDNA. Two constructs were made, differing by their identity with the modified 3A4 N-terminal sequence (E. M. J. Gillam, T. Baba, B-R. Kim, S. Ohmori, and F. P. Guengerich, (1993) Arch. Biochem. Biophys. 305, 123-131). The first modified sequence (3A5#1) was identical to recombinant P450 3A4 up to codon 15, the 3A5 sequence being introduced thereafter. In the other (3A5#2), the successful 3A4 N-terminal nucleotide sequence was attached to codon 30. The yield was greater than fourfold higher in the first construct [up to 260 nmol (liter culture)-1]. The recombinant P450 3A5 (construct 1) was purified to electrophoretic homogeneity using a variation of a three-step procedure developed previously for P450 3A4, with an overall yield of approximately 40%. Purified P450 3A5 was active in nifedipine oxidation, testosterone 6 beta-hydroxylation, aflatoxin 3 alpha-hydroxylation and 8,9-epoxidation, ethylmorphine N-demethylation, erythromycin N-demethylation, and d-benzphetamine N-demethylation. The reconstitution of nifedipine oxidation, testosterone 6 beta-hydroxylation, and the aflatoxin oxidation activities showed dependence upon the presence of cytochrome b5, divalent cations, phospholipid mixtures, glutathione, and cholate similar to that previously found for purified P450 3A4. However, rates of the N-demethylations of ethylmorphine, erythromycin, and d-benzphetamine were as high or higher for P450 3A5 than P450 3A4 and were not particularly dependent upon modifications of reconstitution systems [corrected].

Amino Acid Sequence↗
PubMed1995

Bioactivation of aromatic amines by recombinant human cytochrome P4501A2 expressed in Ames tester strain bacteria: a substitute for activation by mammalian tissue preparations.

The most widely used bioassay in genetic toxicology is the Ames test, which combines a bacterial mutagenicity assay (reversion of Salmonella typhimurium histidine-auxotrophic tester strains) with an exogenous bioactivation system (hepatic postmitochondrial supernatant or "S9"). The enzymatic activities of S9 prepared from the tissues of experimental animals are difficult to control. We show that the requirement for S9 can be obviated by the engineered expression of enzymes of bioactivation within the bacterial cell. With this strategy, reactive metabolites are produced inside the bacterial cell, proximate to the genetic target. Species boundaries can be crossed, and chimeric or mutant enzymes can be studied. We have constructed an Ames tester strain, expressing both aromatic amine N-acetyltransferase and human cytochrome P4501A2, which detects aromatic amine mutagenicity in the absence of S9.

Acetyltransferases↗
PubMed1995

Quantitative investigation of in vitro flow using three-dimensional colour Doppler ultrasound.

A quantitative in vitro flow study was performed by using a three-dimensional colour Doppler imaging system. This system was based on a clinical ultrasound instrument with its transducer mounted on a motor-driven translation stage. A vascular and tissue-mimicking phantom containing two wall-less vessels, one normal and another stenotic, was used to quantify the measurement accuracy of the flow velocity and the flow field. Steady state flows, having Reynolds numbers ranging between 460 and 1300, were generated by a computer-controlled positive displacement pump. Effects of the parameter settings of the ultrasound instrument on results of the estimation of flow field were also studied. Experimental results show that our three-dimensional colour Doppler system's velocity accuracy was better than 7% of the Nyquist velocity and its spatial accuracy was better than 0.5 mm. The system showed a good correlation (r = 0.999) between the estimated and the true mean flow velocity, and a good correlation (r = 0.998) between the estimated maximum and the true mean flow velocity. This study is our first step toward validating the measurement of the three-dimensional velocity and wall shear stress distributions by using three-dimensional colour Doppler ultrasound

Blood Flow Velocity↗
PubMed1995

Toxicological and chemical evaluation of emissions from carpet samples.

This study investigated findings that the off-gassing of certain carpets caused sensory and pulmonary irritation, changes in neurobehavioral signs, and death in exposed mice. Two standard test method measures--one for estimating sensory irritancy (ASTM-E981-84), the other for evaluating the neurotoxic potential of chemicals (functional observational battery)--were coupled with a postmortem assessment to ascertain the mechanism of toxicity. The postmortem evaluation included measurements of hemoglobin, serum clinical chemistries, blood and lung lavage white cell counts and differential, organ weights, and a gross necropsy with a microscopic evaluation of all major organs. The study evaluated three treatment groups composed of two preheated carpet emission exposures and one preheated air-control exposure. No toxic effects were associated with exposure to the off-gassing of the two tested carpets. Clinical chemistry and histopathological alterations were observed with exposure to either filter-air or carpet when compared to nonexposed unrestrained control mice, indicating that the exposure procedure caused significant effects unrelated to carpet emissions. A detailed chemical and microbial evaluation of the carpets and carpet emissions showed volatile organic compounds, pesticide residues, and microbiological flora, but at insufficient quantities to result in acute toxicity. Based on this assessment, there was no indication that exposure to emissions from these two carpets poses a serious health risk.

Air Pollution, Indoor↗
PubMed1995

Phospholipid composition of Pneumocystis carinii carinii and effects of methylprednisolone immunosuppression on rat lung lipids.

The phospholipid class composition of Pneumocystis carinii carinii freshly isolated from infected lungs generally resembled that of the host lung, suggesting that the parasite scavenges lung alveolar lipids. However, subtle quantitative differences were demonstrated, indicating that the pathogen has the metabolic capacity to de novo synthesize, or at least tailor, its lipids. The concentration of phosphatidylcholine, the major lung surfactant lipid, in the organism was lower than that in lungs of normal and immunosuppressed uninfected rats, and the concentration of phosphatidylinositol was higher. Phosphonolipids were not detected in the organism by chemical analysis and nuclear magnetic resonance spectrometry. The immunosuppressive regimen alone caused increases in both surfactant protein A and the lipid content of the whole lung. The lungs of rats that were subjected to corticosteroid immunosuppression and had heavy parasite loads had dramatically elevated surfactant protein A levels, whereas the lipid contents of these lungs were not different from lipid contents in whole lungs of immunosuppressed uninfected rats. P. carinii was found to concentrate lipids, indicating that a large amount of the lipids in the whole infected rat lung was within the parasites residing in the organ. These observations have important implications relevant to the use of corticosteroid therapy for P. carinii pneumonitis.

Animals↗
PubMed1995

3'-end-forming signals of yeast mRNA.

It was previously shown that three distinct but interdependent elements are required for 3' end formation of mRNA in the yeast Saccharomyces cerevisiae: (i) the efficiency element TATATA and related sequences, which function by enhancing the efficiency of positioning elements; (ii) positioning elements, such as TTAAGAAC and AAGAA, which position the poly(A) site; and (iii) the actual site of polyadenylation. In this study, we have shown that several A-rich sequences, including the vertebrate poly(A) signal AATAAA, are also positioning elements. Saturated mutagenesis revealed that optimum sequences of the positioning element were AATAAA and AAAAAA and that this element can tolerate various extents of replacements. However, the GATAAA sequence was completely ineffective. The major cleavage sites determined in vitro corresponded to the major poly(A) sites observed in vivo. Our findings support the assumption that some components of the basic polyadenylation machinery could have been conserved among yeasts, plants, and mammals, although 3' end formation in yeasts is clearly distinct from that of higher eukaryotes.

Actins↗
PubMed1995

Chinese Confucian culture and the medical ethical tradition.

The Confucian culture, rich in its contents and great in its significance, exerted on the thinking, culture and political life of ancient China immense influences, unparalleled by any other school of thought or culture. Confucian theories on morality and ethics, with 'goodness' as the core and 'rites' as the norm, served as the 'key notes' of the traditional medical ethics of China. The viewpoints of Confucianism on benevolence and material interests, on good and evil, on kindheartedness, and on character cultivation were all inherited by the medical workers and thus became prominent in Chinese traditional medical ethics. Hence, it is clear that the medical profession and Confucianism have long shared common goals in terms of ethics. Influenced by the excellent Confucian thinking and culture, a rather highly-developed system of Chinese traditional medical ethics emerged with a well-defined basic content, and the system has been followed and amended by medical professionals of all generations throughout Chinese history. This system, just to mention briefly, contains concepts such as the need: to attach great importance to the value of life; to do one's best to rescue the dying and to heal the wounded; to show concern to those who suffer from diseases; to practise medicine with honesty; to study medical skills painstakingly; to oppose a careless style of work; to comfort oneself in a dignified manner; to respect local customs and to be polite; to treat patients, noble or humble, equally, and to respect the academic achievements of others, etc. Of course, at the same time, Confucian culture has its own historical and class limitations, which exerted negative influences on traditional medical ethics. Now, if we are to keep up with the development of modern medicine, a serious topic must be addressed. That is how to retain the essence of our traditional medical ethics so as to maintain historic continuity and yet, at the same time, add on the new contents of medical ethics so as to incorporate modern features into our system. Therefore, when trying to reform medical practice in China, we are faced with the urgent need to inherit and promulgate the essence of Confucian ethics--discarding its obsolete concepts--while at the same time building up the new medical ethics that can meet the requirements of the outside world and the future.

Beneficence↗
PubMed1995

[Cerebral lesions in AIDS: what can be expected from scintigraphy? Cerebral tomographic scintigraphy using thallium-201: a contribution to the differential diagnosis of lymphomas and infectious lesions].

CT and MRI are not consistently able to differentiate central nervous system (CNS) lymphoma from focal cerebral infection such as toxoplasmosis in the human immunodeficiency virus (HIV) involvement. In this study thallium 201 (and/or technetium-MIBI) SPECT was performed in 6 patients suffering from AIDS and CNS lesions. An index based on the ratio of thallium uptake in the lesion vs the contralateral scalp was calculated. In 4 out of 5 patients with lymphoma (3 confirmed by biopsy, 2 highly suspected on CT and resistance to antitoxoplasmosis treatment) focal lesions showed high uptake of thallium. On the other hand one markedly necrotic lymphoma and all infectious lesions did not take up thallium. This suggests a role for thallium 201 brain SPECT in the workup of focal CNS lesions in AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1995

[Placental ureaplasma urealyticum infection and low birth weight].

Ureaplasma urealyticum (UU) infection during pregnancy may result in poor outcome. Placentae from 116 normal healthy pregnancies were cultured for UU with a recovery rate of 28.45%. 94 cases ended by normal vaginal delivery had a UU positive rate of 29.79%. The UU positive rate of 22 placenta from cases by cesarean section was 22.73%. The 2 positive rates showed no difference of significance (P > 0.05). This result indicated that UU infection of the placenta was present before passing through the birth canal and not due to contaminant during delivery. The birth weight of the neonates with positive UU infection was on the average 2,919g, while that in the negative UU cases was 3,490g, being 571g higher than in the positive group (P < 0.01). This study showed that placental infection with UU is associated with a low birth weight.

Adult↗
PubMed1995

[Detection of pathogenic Entamoeba histolytica DNA in liver abscess aspirates with polymerase chain reaction].

Polymerase chain reaction (PCR) was used to diagnose amebic liver abscess by detecting pathogenic Entamoeba histolytica DNA in liver aspirates from patients with liver abscess. Oligonucleotide primers specific for gene encoding of the 30,000 molecule of pathogenic Entamoeba histolytica were used in the test. Liver aspirates from 23 cases with amebic liver abscess as evidenced by typical clinical findings or very high titres of anti-E. Histolytica antibodies with ELISA were found to be positive with PCR. Fourteen control samples (3 cases of bacterial liver abscess, 1 of liver cancer and 10 of abscess in other sites) were all negative to PCR. The results suggest that PCR is a sensitive and useful method for diagnosing amebic liver abscess.

Animals↗
PubMed1995

[Protective effects of vitamin E on impaired neutrophil phagocytic function in patients with severe burn].

The protective effects of vitamin E on impaired neutrophil phagocytic function were observed in 22 patients with severe burn. The results showed that lowering of SOD values, elevation of MDA values significantly elevated and impairment of neutrophil phagocytic function were all more marked in the patients who did not receive vitamin E than that of vitamin E treated groups and the healthy control. It was also found that there was a significant inverse correlation between MDA values of blood plasma and neutrophil phagocyte rate and phagocyte index in the patients without vitamin E treatment. The results suggested that in severely burned patients the use of free radical scavenger and antioxidant could protect the neutrophil function to certain extent. The optimal dosage of vitamin E will be further assessed.

Adolescent↗
PubMed1995

[Multiple organ injury after delayed fluid resuscitation in severely scalded rats: role of oxygen free radicals].

Sixty gnotobiotic rats with 5 strains of bacteria in intestine were randomized to 4 groups: (1) Sham injury group (controls, n = 6). (2) Early fluid resuscitation (EFR) group (n = 24), receiving fluid resuscitation (Parkland formula) immediately after scald (40% TBSA, third degree). (3) Delayed fluid resuscitation (DFR) group (n = 24) receiving resuscitation 6 hours later after scald. (4) Treatment group (n = 12) receiving DFR and the therapy of VitC and VitE. At 8, 24, 48 and 72 hours after injury, the animals (n = 6, at each point) were sacrificed and the content of oxygen free radicals (OFR), SOD,GSHPx and MDA in the heart, liver, kidney and lung were determined. Morphological Changes of organs, PaO2, PaCO2 and the content of serum CPK, LDH, GPT, GOT, BUN and Cr were also examined. Both EFR and DFR groups demonstrated elevated content of OFR and MDA and reduced content of SOD and GSHPx in their organs. Morphological and serological changes were also observed. All these changes were more obvious in DFR group than in EFR group. After the treatment of VitC and VitE, the changes were ameliorated. Our results suggested that DFR induced the production of OFR, resulting in lipid peroxidation and that OFR injury might be one of the main factors in the pathogenesis of multiple organ injury after DFR.

Animals↗
PubMed1995

[The damaging effect of activated human neutrophils on isolated perfused rat lungs--the role of elastase].

Human neutrophil and its elastase play an important role in the pathogenesis of various lung diseases. We investigated the damaging effect of human neutrophils stimulated with PMA (phorbol myristate acetate 10ng/ml) or calcium ionophase A23187 (2ng/ml) on isolated perfused rat lungs. The study specimens consisted of 4 groups of animals. A control, B perfused with human neutrophils, C perfused with human neutrophils stimulated with PMA, and D perfused with human neutrophils stimulated with A23187. By using the ELISA method, we found that the level of human neutrophil elastase (HNE) in perfusate increased significantly at 30min (1.68 +/- 0.79ng/ml P < 0.05) and 60min (2.35 +/- 0.87 ng/ml P < 0.01) after PMA stimulating, but the HNE in the lung lavage fluid of the same group only slightly increased and the concentration of protein in lavage fluid did not change. After stimulating with A23187, the concentration of HNE in perfusate increased markedly at 30min (4.03 +/- 1.96ng/ml P < 0.01) and maintained at high level (P < 0.01). There was a significant increase of HNE level in lung lavage fluid (2.49 +/- 0.61ng/ml) from group D rat lungs, compared with group A, B or C, and the protein as well (1.61 +/- 0.58mg/ml P < 0.05). All the results indicate that the stimulated human neutrophils can release elastase in perfused rat lung. Neutrophil stimulated with A23187 can increase pulmonary permeability and injure the lung. We suggest that the lung damage, caused by human neutrophils, may be the effect of neutrophil elastase or the synergistic effect with some other substances derived from neutrophil.

Animals↗
PubMed1995

Extensive wound excision in shock stage in patients with major burns.

To stop excessive plasma loss, alleviate noxious effects of devitalized tissues on the body and shorten the hospitalization time, we performed extensive escharectomy during the shock period in extensively burned patients. Group A consisted of 21 patients aged 9-45 years (26.1 +/- 7.9 years), with a mean total burn area of 63.2% +/- 18.1% TBSA, and full-thickness injury involving 35.9% +/- 19.6% TBSA. The first escharectomy was done at 24.1 +/- 13.9 hours postburn, and excision area averaged 32.3% +/- 6.7% TBSA (24%-46%). In 15 of them, Swan-Ganz catheter was introduced to monitor the hemodynamic changes. It was found that RAP, PAP, PAWP, ABP, HR, CO and CI were all stable during and after the operation. Group B consisted of 29 patients aged 11-50 years (30.4 +/- 11.7 years), in whom escharectomy was begun 4-5 days postburn. The mean healing time of the patients in group A was 33.1 days, shorter than that of group B patients (40.1 days). The duration of hemoconcentration was shorter in group A. The amount of blood transfusion was almost 700 ml less in group A during the first two weeks. Less antibiotics were used with fewer visceral complications in group A. We believe that escharectomy during the burn shock stage is feasible.

Adolescent↗
PubMed1995

[Preparation and identification of monoclonal antibody against sterigmatocystin].

Compound antigen, bovine serum albumin-sterigmatocystin (BSA-ST) or hemocyanin sterigmatocystin (H-ST) was prepared by converting ST to its hemiacetal group in ST and taking ST conjugated to BSA or H. Balb/c mice were immunized with BSA-ST, and then their spleen cells were isolated and fused with SP2/0 murine myeloma cells. A hybridoma cell strain that could stably secrete monoclonal antibody against ST (McAb-ST) was selected, and both of their ascites and serum were rich in McAb-ST induced by cells of this strain. McAb-ST was identified as Ig-Gi with a molecular weight of 168,000 kd (53,000 for heavy chain and 31,000 for light one), and with an affinity constant of H-ST reaction of 1.29 x 10(9) mol/L measured by indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). Relative cross reaction of McAb-ST with ST analogues was less than 2%. The minimal 0.5 pg/25 microliters of ST can be detected with IC-ELISA using McAb-ST and ST simultaneously, with a linear range of 0.1-10 ng/ml.

Animals↗