Search PubMed⌕ Search

Biomedical subjects

Z Feng

Publications and source records attributed to Z Feng.

At least 217 records · Page 12Linked to original sources
PubMed1995

A pilot study of DNA aneuploidy in colorectal adenomas and risk of adenoma recurrence.

This case-control study examined whether DNA aneuploidy in colorectal adenomas is a risk factor for subsequent adenoma recurrence. Cases (recurrent polyp formers) were defined as persons with diagnoses of new adenomas at 2 colonoscopies following the index (first) adenoma diagnosis; controls were persons with no new adenomas at a follow-up at least 1 year after the index diagnosis. Cases (n = 22) and up to 3 controls (n = 29) were matched for factors known to be associated with polyp recurrence or aneuploidy: (a) age; (b) histology; (c) number of index polyps; and (d) size of largest index polyp. The largest adenoma from the index colonoscopy was removed from the paraffin block and analyzed for DNA content abnormalities by flow cytometry. On the basis of the observed distribution of aneuploidy in case-control sets, the point estimate for the relative odds of recurrence given aneuploidy in the index polyp was infinity (P < 0.035), and the lower bound for the 95% confidence interval was 2.02. We conclude that in this convenience sample, DNA aneuploidy increased the risk of recurrent colorectal adenomas. Larger, preferably prospective studies are needed before DNA content flow cytometric analysis of colorectal adenomas can be recommended as a routine clinical practice, but these results do suggest that polyp ploidy should be assessed in research studies using adenomas as end points or intermediate end point markers.

Adenoma↗
PubMed1995

Regulation of the translation and processing of rat dopamine beta-hydroxylase by metal ions in a cell free system.

Metal ions play an important role in the metabolism of prokaryotic and eukaryotic cells. In this study we examine the effect of various metal ions on the translation, glycosylation and co-translational processing of dopamine beta-hydroxylase (DBH) in vitro. The translation of wild type DBH mRNA and constructs with site directed mutations near the putative signal cleavage site was carried out with the addition of different ions (Mg2+, Cu2+, Mn2+, Ni2+, Co2+, Zn2+, Pb2+, Fe2+, Fe3+, Ca2+) in a cell-free system in the present of microsomal membranes. Most of the metal ions inhibited translation at concentrations above 1.5 mM. The translation was more sensitive to Fe2+ than Fe3+. Ni2+ and Cu2+ preferentially inhibited formation of the glycosylated products. Only magnesium affected the ratio of the two different processed forms in a concentration dependent manner.

Animals↗
PubMed1995

Dietary intake and exposure to environmental tobacco smoke in a worksite population.

OBJECTIVES: Nonsmokers who live with smokers have poorer dietary habits than those who live in nonsmoking households. This relationship may be due to shared lifestyle patterns by spouses and family members. However, in order to fully understand the nature of this relationship, it is also important to examine the association between diet and exposure to environmental tobacco smoke (ETS) at the workplace. Further, blue collar workers' patterns of exposure to ETS both at work and at home have not been studied. The goal of this study is to examine the dietary intake of manufacturing workers as it relates to exposure to ETS at work and at home. METHODS: The Working Well Trial surveyed 10,833 nonsmokers about a variety of health behaviors, including smoking, dietary behaviors, and ETS exposure. RESULTS: Nonsmokers who had ETS exposure in their household had significantly lower intake of all target micronutrients, compared to those without household exposure. Exposure to ETS at the workplace was associated with lower intakes of vitamin C and fruits and vegetables, but not the other micronutrients examined. CONCLUSIONS: Exposure to ETS was associated with poorer dietary habits. Household exposure was a stronger predictor of intake than was workplace exposure. Because of the antagonistic effects of many components of a healthful diet in relation to the harmful effects of tobacco smoke, these findings have relevance larger than either ETS exposure or diet considered singly.

Adult↗
PubMed1995

ETS exposure in the workplace. Perceptions and reactions by employees in 114 work sites. Working Well Research Group [corrected].

Employees are often exposed to and bothered by environmental tobacco smoke (ETS) in the workplace; however, little is known about correlates of workers' perceptions of their exposure. In this study, 20,801 employees in 114 work sites in the United States were surveyed; variables related to perceptions of exposure and being bothered by ETS were entered into regression models. Many of the workplaces had total or partial restrictions on smoking in the workplace; however, over half of the respondents (52.4%) reported they were exposed to ETS at work. Smoking policy, smoking status, age, gender, living with a smoker, and occupation contributed to models for perceived exposure and being bothered by tobacco smoke. Work site smoking restrictions seem to have an impact on employee attitudes concerning exposure to ETS. About 35% of employees were bothered regularly by smokiness at their workplaces, which made their working conditions both uncomfortable and exposed them to an unsafe working environment.

Adult↗
PubMed1995

[The sensitizing role of the anti-idiotypic monoclonal antibody-NP30 of Schistosoma japonicum in egg granuloma formation].

C57BL/6 mice sensitized intraperitoneally with the anti-idiotypic monoclonal antibody-NP30 of Schistosoma japonicum and then injected with vital egg suspension directly into spleen were used as the experimental models of hepatic egg granulomas in this study. The soluble egg antigen(SEA) sensitized group was used as positive control and the SP2/0 ascites injected group as negative control. The results showed that the size and volume of hepatic egg granulomas in the NP30 sensitized group increased obviously 4 days after egg injection and that a large number of eosinophiles appeared in egg granulomas. The size and volume of egg granulomas reached the peak values at d8 and d15 after egg injection, respectively. The peak values of the NP30 sensitized group were similar to those of the SEA sensitized group (P > 0.05). The size and volume of egg granulomas in the SP2/0 ascites injected group did not reach the peak values, which were less than those of the group sensitized with NP30 (size: P < 0.05; volume: P < 0.01), until d32 after egg injection. Our study suggests that NP30 may play a sensitizing role in the formation of hepatic egg granulomas.

Animals↗
PubMed1994

Brain abscess due to Pasteurella multocida.

The patient was a 26-year-old man who complained of headache and vomiting. On examination, there was nothing abnormal, but the edge of the right optic papilla was not clear. His temperature was 38.5 degrees C, pulse 96/min, blood pressure 120/80 mmHg. A space-occupying lesion in his fronto-dextra cupular part was found by CT scanning. He had a 12-year history of chronic purulent otitis. The diagnosis was a brain abscess in the fronto-dextra cupular part. The brain abscess was extracted and Pasteurella multocida was isolated from the dark brown pus draining from the abscess. The patient recovered through proper antibiotic therapy based on a sensitivity test. Reports of infections caused by this organism in foreign countries very widely from local infections due to bites and scratches by cats, dogs etc. to general infections such as infections of the respiratory tract, sepsis and meningitis. However, Pasteurella multocida brain abscesses are rare. Pasteurella multocida is a Gram-negative short rod which is best known as part of the mouth flora and as a pathogen causing septicemia in many domestic animals, such as cats, dogs etc.. Infection in man results mainly from animal bites or scratches. It has been reported that Pasteurella multodida can cause human septicemia, meningitis, respiratory tract infection, conjunctivitis and other infections. We isolated a strain of Pasteurella multocida from the pus of a brain abscess following chronic purulent otitis on August 6, 1990.

Adult↗
PubMed1994

Inhibition of expression of delayed hypersensitivity by neutralizing monoclonal anti-T-cell fibronectin antibody.

T-cell fibronectin (FN) is a unique cellular FN that is rapidly synthesized by memory T cells in response to antigen. Monoclonal anti-T-cell FN antibodies have been used to clarify the role of T-cell FN in the in vivo expression of delayed hypersensitivity. IgGl(kappa) mouse anti-human T-cell FN monoclonal antibodies 231 and 248 recognized epitopes on the FN cell-binding domain, were cross-reactive with plasma FN, and neutralized human and guinea-pig T-cell FN monocyte agglutinating activity. When injected intradermally together with tuberculin or 30 min before topical application of reactive sensitizer, antibody 231 significantly decreased macroscopic expression of guinea-pig delayed hypersensitivity at 24 hr in a dose-dependent manner. Similar doses of antibody 248 caused a slight statistically non-significant enhancement of delayed-type hypersensitivity (DTH) expression. Inhibition of visible skin responses was not associated with qualitative or quantitative changes in cellular infiltrates at the reaction site. Antibody 231 modulated expression of delayed hypersensitivity in a qualitatively and quantitatively similar manner to the FN-binding mycobacterial antigen 85 proteins. This is consistent with anti-T-cell FN and antigen 85 acting on the same molecule in vivo.

Agglutination↗
PubMed1994

Comparative observation on effect of electric acupuncture of neiguan (P 6) at chen time versus xu time on left ventricular function in patients with coronary heart disease.

Paired experimental design was adopted in this experiment for comparative observation on effect of electric acupuncture (EA) of Neiguan (P 6) at Chen Time (7 a.m. to 9 a.m.) versus Xu Time (7 p.m. to 9 p.m.) on left ventricular function in patients with coronary heart disease (CHD). The results show that EA performed at Chen Time could improve the left ventricular function of CHD patients as indicated by shortening of PEPI and decrease of PEPI/LVETI ratio; on the contrary, EA performed at Xu Time prolonged PEPI and raised PEPI/LVETI ratio in CHD patients, suggesting impairment of left ventricular function.

Acupuncture Points↗
PubMed1993

Enantioselective antiplatelet actions of nipecotamides.

Two synthetic racemic nipecotamides, 1-decyl-3-(N,N- diethylcarbamoyl)piperidine hydrobromide (1) and alpha, alpha'-bis[3-(N-benzyl-N-methylcarbamoyl)piperidino]-p-xylene dihydrobromide (2) were resolved on a chiral alpha 1-acid glycoprotein semipreparative HPLC column. Thus, rac.1 was resolved into two enantiomers 1A-(+) and 1B-(-); rac.2 was separated into the optical antipodes 2A-(-) and 2C-(+), and the meso diastereomer 2B-(0). Also on a preparative scale, 97% pure 2C was obtained via diastereomeric salt formation using dibenzoyl-L-(-)-tartaric acid. The individual isomers were evaluated for their platelet aggregation inhibitory potency. In inhibiting ADP-induced aggregation of human platelets in vitro, 1B-(-) was 4 times more potent than its optical antipode 1A-(+), and 2C-(+) was 6 times as active as 2A-(-); the meso diastereomer 2B-(0) had intermediate activity. With collagen as the 1B-(-) was twice as active as 1A-(+), and 2C-(+), the most active compound in this series (IC50 = 0.96 microM), was 10 times more potent than its antipode 2A-(-). Again, the meso diastereomer 2B-(0) had intermediate activity. These results demonstrate the enantioselective antiplatelet actions of mono- and bis- nipecotamide derivatives.

Adenosine Diphosphate↗
PubMed1993

Pfs2400 can mediate antibody-dependent malaria transmission inhibition and may be the Plasmodium falciparum 11.1 gene product.

Monoclonal antibodies (mAb) have been raised against Plasmodium falciparum gametocyte stage protein extracts, in an effort to identify novel parasite antigens that might mediate malaria transmission-blocking immunity. mAb 1A1 identified Pfs2400, a sexual stage-specific antigen of greater than 2 megadaltons, that is associated with the outer leaflet of the parasitophorous vacuole membrane in mature circulating gametocyte-infected red blood cells. Upon induction of gametogenesis, Pfs2400 partitions between the gamete plasmalemma and the degenerating erythrocyte membrane. The antigen is no longer detectable in the fully emerged gamete. mAb 1A1 dramatically reduces the number of oocysts formed in P. falciparum gametocyte-fed mosquitoes. The cognate antigen is probably the product of the Pf11.1 gene (Scherf et al. 1988. EMBO [Eur. Mol. Biol. Organ.]J. 7:1129) on the basis that a peptide composed of two copies of the degenerate nine amino acid repeat sequence in the Pf11.1 protein, can inhibit binding of mAb1A1 to the native antigen. The mechanism of transmission inhibition mediated by the Pfs2400 is discussed.

Amino Acid Sequence↗
PubMed1993

Importance of lysine and arginine residues to the biological activity of trichosanthin, a ribosome-inactivating protein from Trichosanthes kirilowii tubers.

Lysine and arginine residues in trichosanthin were modified with ethyl acetimidate and phenylglyoxal, respectively. The effects of these chemical modifications on the cell-free protein-synthesis-inhibitory activity and the antigen-antibody (Ag-Ab) interaction between trichosanthin and its antibody were examined. Ethyl acetimidate modification abolished the protein-synthesis-inhibitory activity of trichosanthin. The inactivation process followed simple first-order kinetics with an inactivation half-life of about 18.5 min. Modification of one lysine residue seemed to be responsible for such inactivation. Arginine modification also inactivated trichosanthin. The inactivation process, however, was biphasic with inactivation half-lives of approximately 15 and 540 min. Arginine modification of trichosanthin had little or no effect on Ag-Ab interaction, whereas lysine modification slightly but significantly weakened Ag-Ab binding.

Arginine↗
PubMed1992

Glycosylation and membrane insertion of newly synthesized rat dopamine beta-hydroxylase in a cell-free system without signal cleavage.

Dopamine beta-hydroxylase (DBH, EC 1.14.17.1) is present in both membrane-bound and soluble forms in neurosecretory vesicles. This study was designed to investigate the differences between membrane-bound and soluble DBH and how they may arise from translation of a single mRNA. Antisera to a peptide corresponding to the carboxyl terminus of rat DBH was found to specifically immunoprecipitate the 77- and 73-kDa subunits of newly synthesized DBH in rat brain. Thus, both soluble and membrane-bound forms contain the same carboxyl terminus. To investigate differences at the amino terminus, full-length rat DBH mRNA, translated in a cell-free system, produced a 66-kDa peptide. An additional higher molecular mass product was synthesized upon co-translational addition of microsomal membranes. This product was glycosylated since it bound to concanavalin A-Sepharose and reverted to the 66-kDa polypeptide after treatment with endoglycosidase H. This glycosylated product was resistant to protease digestion and fractionated with microsomal membranes on sucrose gradients, indicating that it is incorporated into the microsomal membranes. Amino-terminal sequencing of the glycosylated translation product indicated that the amino-terminal "signal" sequence was not cleaved. The results indicate that in the cell-free system newly synthesized DBH undergoes glycosylation and incorporation into microsomal membranes without cleavage of the NH2-terminal signal sequence.

Amino Acid Sequence↗
PubMed1992

Chiral separation of nipecotic acid amides.

1-Decyl-3-(N,N-diethylcarbamoyl)piperidine (1) and alpha,alpha'-bis[3-(N-benzyl-N-methylcarbamoyl)piperidinol]-p-xyle ne (2) represent mono-N-substituted and bis-N-substituted carbamoylpiperidines, or nipecotic acid amides, respectively. Initially, several attempts were made to resolve these compounds using beta-cyclodextrin, cellulose carbamate and Pirkle-type columns. However, the interactions of the stereoisomers of the two compounds with these stationary phases did not differ enough to permit satisfactory separations. Baseline resolution was achieved using an alpha 1-acid glycoprotein (AGP) chiral column. The mobile phase was phosphate buffer (pH 7.0). Tetrabutylammonium (TBA) was used as the cationic modifier and ethanol as the uncharged modifier. Circular dichroism was used to identify the enantiomers. Compound 1 was resolved into positive and negative enantiomers and 2 into positive and negative enantiomers and a meso diastereomer. The influence of pH, buffer ionic strength, cationic and uncharged modifier concentrations on retention, chiral selectivity and resolution were evaluated. Based on the results, it is suggested that both ionic and hydrophobic interactions may be responsible for retention and resolution.

Buffers↗
PubMed1992

Correlated binomial variates: properties of estimator of intraclass correlation and its effect on sample size calculation.

In group randomized studies, the sample size calculations are complicated by within group (worksite, community, etc.) correlation. We compare by simulation the moment method and the more standard ANOVA method of estimating the intraclass correlation. We find the former is less biased for a small to moderate number of clusters but the difference disappears when the appropriate degree of freedom is used for the ANOVA estimator. We propose a simulation approach for sample size determination and illustrate it with an example.

Analysis of Variance↗
PubMed1992

Molecular determinants of the platelet aggregation inhibitory activity of carbamoylpiperidines.

A series of alpha,alpha'-bis[3-(N,N-dialkylcarbamoyl)piperidino]-p- xylenes were synthesized and tested for their inhibitory activity on ADP-induced aggregation of human platelets. A parabolic curve was obtained when log 1/C (activity) was plotted against log P (octanol/water partition coefficient). Using this as a model, a new analogue, alpha,alpha'-bis-[3-(N-methyl-N-butylcarbamoyl)piperidino]-p-xylen e (3g), was synthesized with a predicted IC50 of 25 microM. When this compound was subsequently evaluated, the IC50 was 22.1 +/- 5.5 microM, demonstrating the applicability of this model. The amide oxygen of the carbamoyl substituent appeared necessary for activity. Thus, for example, when the amide carbonyl group of 3a (IC50 = 44.5 microM) was reduced to CH2, the resulting compound 4 had a dramatically reduced activity, IC50 = 1565 microM. Compound 3a was resolved into (+) and (-) enantiomers and a meso (0) diastereomer using fractional crystallization, diastereomeric tartrate formation, and chiral HPLC. Compared to (-)-3a, the (+) isomer was 15 times more potent when ADP was the agonist and 19 times more active when collagen was used as the agonist. Molecular modeling of R,R- and S,S-3a using the SYBYL program was used to examine their interactions with phosphatidylinositol (PI). There was a better fit between PI and the R,R-3a with the energy of interaction being 17.6 kcal/mol less than that of the S,S-3a/PI complex. Although the absolute stereochemistry of individual enantiomers is not known, this study shows that R,R-3a interacts more favorably with PI than does S,S-3a and that (+)-3a is a more potent inhibitor of human platelet aggregation than (-)-3a. It is postulated that because of their lipophilicity, these compounds penetrate the platelet membrane and are then protonated at the pH of the cytosol. The protonated N then neutralizes the anionic charge on the membrane phosphoinositides, thereby rendering them less susceptible to hydrolysis by phospholipase C. Thus, the determinant parameters for optimum antiplatelet activity in 3-carbamoylpiperidines are (1) the amide carbonyl, (2) appropriate stereochemistry of the 3-substituent and (3) a log P value of about 4.5.

Adenosine Diphosphate↗