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Biomedical subjects

Z Feng

Publications and source records attributed to Z Feng.

At least 181 records · Page 10Linked to original sources
PubMed1997

Carbon isotopic composition, gas exchange, and growth of three populations of ponderosa pine differing in drought tolerance.

Effects of water supply on gas exchange, carbon isotopic composition, and relative growth rate were compared among seedlings from three populations of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) grown in a controlled environment chamber. The three populations were chosen to represent high, moderate and low drought tolerance. There was no indication that drought tolerance was related to high water-use efficiency. Populations differed (P < 0.05) in relative growth rate (RGR), but did not differ (P > 0.10) in gas exchange variables or carbon isotope ratio (delta(13)C). Well-watered seedlings had significantly higher RGR, xylem pressure potential (Psi(xpp)), net photosynthesis (A), stomatal conductance to water vapor (g), and lower delta(13)C and instantaneous water-use efficiency than water-stressed seedlings. With decreasing Psi(xpp), A decreased linearly, whereas g decreased exponentially. Seedlings of the highly drought-tolerant population were more sensitive to water availability than seedlings from the other populations; they used water quickly when water was available, but closed their stomata in response to water stress. We conclude that, in ponderosa pine, the drought avoidance mechanism is more important for survival and growth in arid and semiarid environments than the efficient use of water.

Journal Article↗
PubMed1997

Overexpression of the D-alanine racemase gene confers resistance to D-cycloserine in Mycobacterium smegmatis.

D-Cycloserine is an effective second-line drug against Mycobacterium avium and Mycobacterium tuberculosis. To analyze the genetic determinants of D-cycloserine resistance in mycobacteria, a library of a resistant Mycobacterium smegmatis mutant was constructed. A resistant clone harboring a recombinant plasmid with a 3.1-kb insert that contained the glutamate decarboxylase (gadA) and D-alanine racemase (alrA) genes was identified. Subcloning experiments demonstrated that alrA was necessary and sufficient to confer a D-cycloserine resistance phenotype. The D-alanine racemase activities of wild-type and recombinant M. smegmatis strains were inhibited by D-cycloserine in a concentration-dependent manner. The D-cycloserine resistance phenotype in the recombinant clone was due to the overexpression of the wild-type alrA gene in a multicopy vector. Analysis of a spontaneous resistant mutant also demonstrated overproduction of wild-type AlrA enzyme. Nucleotide sequence analysis of the overproducing mutant revealed a single transversion (G-->T) at the alrA promoter, which resulted in elevated beta-galactosidase reporter gene expression. Furthermore, transformants of Mycobacterium intracellulare and Mycobacterium bovis BCG carrying the M. smegmatis wild-type alrA gene in a multicopy vector were resistant to D-cycloserine, suggesting that AlrA overproduction is a potential mechanism of D-cycloserine resistance in clinical isolates of M. tuberculosis and other pathogenic mycobacteria. In conclusion, these results show that one of the mechanisms of D-cycloserine resistance in M. smegmatis involves the overexpression of the alrA gene due to a promoter-up mutation.

Alanine Racemase↗
PubMed1997

A dietary intervention in primary care practice: the Eating Patterns Study.

OBJECTIVES: This study evaluated the effectiveness of a low-intensity dietary intervention in primary care practice in lowering dietary fat intake and raising dietary fiber intake. METHODS: A randomized controlled trial of 28 physician practices in six primary care clinics enrolled, by telephone, adult patients who had appointments for nonurgent nonacute visits. Of 3490 eligible patients contacted, 2111 completed baseline interview; 86.1% also completed a 12-month follow-up. Physicians gave intervention participants a self-help booklet and a brief motivational message. Changes in fat and fiber from baseline to 12-month follow-up were evaluated. RESULTS: Intervention and control groups both reported a decrease in fat intake and an increase in fiber intake. The differential change and 95% confidence interval (CI) for the percentage of energy obtained from fat was -1.2 (CI = -0.71, -1.7) (P = .0015), for grams fiber/1000 kcal 0.32 (CI = -0.066, 0.71) (P = .086), for fat score -0.044 (CI = -0.016, -0.072) (P = .010), and for fiber score 0.036 (CI = 0.011, 0.061) (P = .014), with greater reductions in fat and greater increase in fiber in the intervention group. CONCLUSIONS: This low-intensity intervention was effective in dietary behavior change.

Adult↗
PubMed1997

Effect of artemether on glucose uptake and glycogen content in Schistosoma japonicum.

AIM: To study the effect of artemether (Art) on glucose uptake and glycogen content in schistosomes. METHODS: Schistosomes recovered from mice treated intragastrically with Art 300 mg.kg-1 for 24-48 h, were incubated in the drug-free medium containing [U-14C]glucose 11.1 MBq.L-1. The glycogen content, [U-14C]glucose uptake, and incorporation of [U-14C]glucose into worm glycogen in both male and female worms were determined. RESULTS: When above-mentioned schistosomes were exposed to drug-free medium containing [U-14C]glucose for 1-24 h, the glycogen contents of male and female worms decreased 27%-61% and 39%-78%, respectively. Only 3 out of 6 male worm groups showed 23%-35% decrease in glucose uptake, while much less glucose uptake was found in female worms in all groups with reduction rates of 18%-38%. Apart from 2 male groups no apparent change in the incorporation of [U-14C]glucose into the worm glycogen was seen. CONCLUSIONS: Art-induced glycogen reduction in schistosomes was related to an inhibition of glycolysis rather than an interference with glucose uptake.

Animals↗
PubMed1997

[Antiviral effect of antisense oligodeoxynucleotides complementary to hepatitis B virus X gene in vitro].

It has been reported that the products of the human hepatitis B virus (HBV) X genes can transactivate a variety of viral and host promoters including the X, core, pre S2/S and pre S1 promoter. In order to investigate their antiviral effect in cell culture, three pieces of antisense phosphorothioate oligodeoxynucleotides (ASON) complementary to HBV X genes 1510-1530, 1555-1581, 1768-1791 regions were synthesized. The specificity of the inhibitory effect of the ASON was determined by using 2, 2, 15 cells by ELISA, PAP-ELISA and in situ hybridization to detect HBsAg, HBeAg, HBxAg and HBV DNA. The results showed that these ASON could inhibit the expression of HBxAg, as well as HBsAg and HBeAg, with the inhibitary rates of 78.07%, 80.65% and 62.76% respectively. In situ hybridization results indicated that HBV DNA replication can also be inhibited. The decrease in virus production and the ammount of HBV DNA were dose and time dependent. The mechanism of action may be due to the inhibition of HBxAg by sequences specific to ASON, and then the decrease of its transactivating effect for HBV DNA promoter.

DNA Replication↗
PubMed1997

[Fracture toughness of cortical bone in tension, shear, and tear--a comparison of longitudinal and transverse fracture].

The fracture toughness at crack initiation was determined for bovine cortical bone under tension (mode I), shear (mode II), and tear (mode III). A total of 130 compact tension specimens, compact shear specimens and triple pantleg specimens were used for the measurement of fracture toughness under tension, shear, and tear, respectively. Multiple-sample compliance method was utilized to measure the critical strain energy release rate (Gc) at the a/W = 0.55 (crack length, a, to specimen width, W, ratio). The critical stress intensity factor (Kc) was also calculated from the critical loading (PQ) of the specimens at the a/W = 0.55. The effect of the anisotropy of bone on its resistance to crack initiation under shear and tear loading was investigated as well. The fracture toughness of bone with precrack orientations parallel(designed as longitudinal fracture) to and that with precrack orientations normal (designed as transverse fracture) to the longitudinal axis of bone were compared. In longitudinal fracture, the critical strain energy release rates(Gc) of cortical bone under tension, shear, and tear were 644 +/- 102, 2430 +/- 836, and 1723 +/- 486 N/m, respectively. In transverse fracture, the critical strain energy release rates(Gc) of cortical bone under tesion, shear, and tear were 1374 +/- 183, 4710 +/- 1284, and 4016 +/- 948 N/m, respectively. An analysis of variance demonstrated that the crack initiation fracture toughness of bone under shear and tear loading is significantly greater than that under tensile loading in both longitudinal and transverse fracture. Our results also suggest that cortical bone has been "designed" to prevent crack initiation in transverse fracture under tension, shear, and tesar.

Animals↗
PubMed1997

Milk accumulation triggers apoptosis of mammary epithelial cells.

Continuous milk production is a consequence of a complex interplay of lactogenic hormones and it depends on the suckling stimulus during lactation. Involution is associated with a massive engorgement of the gland with milk followed by apoptosis of secretory epithelial cells and a restructing of the gland. Sealing of a single gland during lactation is sufficient to induce an initial engorgement and a subsequent collapse of alveolar structures and massive epithelial cell death while the other glands of the same animal remain morphologically and functionally in a lactating state. Many markers of involution such as sulfated glycoprotein-2, protein kinase A, transcription factor AP-1 and most notably stromelysin are induced in sealed glands. These findings suggest a cell death pathway which is independent of the systemic levels of lactogenic hormones but which is triggered by an accumulation of apoptosis-inducing factors in the milk, in the lobulo-alveolar structures or by a physical distortion of secretory epithelial cells generated by the engorgement.

Animals↗
PubMed1997

Studies on efficacy of praziquantel and mebendazole-medicated salt in treatment of Echinochasmus fujianensis infection.

The therapeutic effect of praziquantel and mebendazole-medicated salt has been studied in 109 cases with Echinochasmus fujianensis infection. These cases were randomly divided into four groups: 2 groups with a single dose of praziquantel 5 mg/kg or 2.5 mg/kg; and other 2 groups with mebendazole 800mg or 400 mg in 10d table salt. Four weeks after treatment, the egg negative conversion rates were 100%, 92.3%, 85.2% and 71.4% respectively, the egg reduction rates were 84.8-100%, and side-effects were mild. The symptoms caused by infection such as abdominal pain, diarrhea, distension and anorexia were obviously relieved. These data indicated that praziquantel is the drug of choice in the treatment of Echinochasmus fujianensis. The dosage is only 2.5 mg/kg, and its egg negative conversion rate and reduction rate reach 92.3% and 95.4%, respectively. For convenience, the dosage can be made according to their age. Children under 12 take half a tablet (100 mg), and one tablet (200 mg) for those over 12. This dosage is approximately equal to 2.5-5.0 mg/kg. Although the efficacy of mebendazole is lower than praziquantel, its egg negative conversion rate also reaches 71.4-85%. Mebendazole-medicated salt can be used for treating Echinochasmus fujianensis infection as the presence of co-infection with nematodes.

Adolescent↗
PubMed1997

[Regulation of myocardium beta-adrenoreceptor pathway in ventricular remodeling of heart failure patients].

OBJECTIVE: To study the role of myocardium beta-adrenoreceptor pathway in ventricular remodeling of heart failure patients. METHODS: Beta-adrenergic receptor density (Bmax) and the content of cAMP were measured in the papillae of left ventricle and blood lymphocyte of 20 patients with heart failure (CHF) (NYHA classification II to III). Bmax was investigated by 3H-dihydroalpneolol as ligand, cAMP by competitive immunoassay, and left ventricle mass index (LVMI) by echocardiogram. RESULTS: The Bmax and cAMP in failing myocardium were significantly negatively were correlated with LVMI (r = -0.77, P < 0.01 and r = -0.46, P < 0.05 respectively). The Bmax of myocardium and blood lymphocyte in CHF patients with NYHA III (63 +/- 12 fmol/mgpro and 514 +/- 115 fmol/10(7) cell), was significantly lower than that of NYHA II patients (94 +/- 20 fmol/mgpro and 702 +/- 138 fmol/10(7) cell, and that in patients with abnormal LVMI (62 +/- 12 fmol/mgpro and 516 +/- 122 fmol/10(7) cell) decreased more significantly than that in normal LVMI patients. Even in normal LVMI patients (92 +/- 21 fmol/ mgpro and 682 +/- 146 fmol/10(7) cell), the Bmax of blood lymphocyte was already decreased (P < 0.01), when comparing with the controls. The intralymphocyte cAMP content was more significantly decreased than that of the controls (P < 0.05). CONCLUSIONS: The Bmax can reflect the severity of ventricle remodeling and the impairment of myocardium. The regulation of myocardium intracellular messenger transduction is earlier than the pathologic structural change of LV remodeling.

Adult↗
PubMed1996

A comparison of statistical methods for clustered data analysis with Gaussian error.

We investigate by simulation the properties of four different estimation procedures under a linear model for correlated data with Gaussian error: maximum likelihood based on the normal mixed linear model; generalized estimating equations; a four-stage method, and a bootstrap method that resamples clusters rather than individuals. We pay special attention to the group randomized trials where the number of independent clusters is small, cluster sizes are big, and the correlation within the cluster is weak. We show that for balanced and near balanced data when the number of independent clusters is small (< or = 10), the bootstrap is superior if analysts do not want to impose strong distribution and covariance structure assumptions. Otherwise, ML and four-stage methods are slightly better. All four methods perform well when the number of independent clusters reaches 50.

Bias↗
PubMed1996

Conformational changes in the Escherichia coli ATP synthase (ECF1F0) monitored by nucleotide-dependent differences in the reactivity of Cys-87 of the gamma subunit in the mutant betaGlu-381 --> Ala.

Cys-87, one of two intrinsic cysteines of the gamma subunit of the Escherichia coli ATP synthase (ECF1F0), is in a short segment of this subunit that binds to the bottom domain of a beta subunit close to a glutamate (Glu-381). Cys-87 was unreactive to maleimides under all conditions in wild-type ECF1 and ECF1F0 but became reactive when Glu-381 of beta was replaced by a cysteine or alanine. The reactivity of Cys-87 with maleimides was nucleotide-dependent, occurring with ATP or ADP + EDTA in catalytic sites, in the presence of AMP.PNP + Mg2+ but not with ADP + Mg2+ bound, whether Pi was present or not, and not when nucleotide binding sites were empty. Binding of N-ethylmaleimide had no effect, whereas 7-diethyl-amino-3-(4'-maleimidylphenyl)-4-methylcoumarin increased the ATPase activity of ECF1 more than 2-fold by reaction with Cys-87. In ECF1F0, these reagents inhibited activity. The nucleotide dependence of the reaction of Cys-87 of the gamma subunit depended on the presence of the epsilon subunit. In epsilon subunit-free ECF1, maleimides reacted with Cys-87 under all nucleotide conditions, including when catalytic sites were empty. These results are discussed in terms of nucleotide-dependent movements of the gamma subunit during functioning of the F1F0-type ATPase.

Base Sequence↗
PubMed1996

Construction of expressing plasmids of recombinant FN polypeptides with bifunctional-domain and the characterization of the products expressed in E. coli.

Two expressing plasmids have been constructed and used to express two bifunctional-domain recombinant polypeptides of human fibronectin (FN) in E. coli. One was CH50 (Pro1239-Ser1515 of FN linked with Ala1690-Thr1960 of FN through Met) and the other was CH56 (Pro1239-Thr1960 of FN). Both of two polypeptides were capable of binding heparin and were purified by heparin-agarose affinity chromatography. The purified products were capable of binding cells. The production of CH50 and CH56 polypeptides provided a fundamental basis for further study of the anti-metastatic function of recombinant fibronectin polypeptides.

Escherichia coli↗
PubMed1996

The individual and combined effects of ozone and simulated acid rain on growth, gas exchange rate and water-use efficiency of Pinus armandi Franch.

The seedlings of Pinus armandi Franch. were exposed to ozone (O(3)) at 300 ppb for 8 h a day, 6 days a week, and simulated acid rain of pH 3.0 or 2.3, 6 times a week, alone or in combination, for 14 weeks from 15 June to 20 September 1993. The control seedlings were exposed to charcoal-filtered air and simulated rain of pH 6.8 during the same period. Significant interactive effects of O(3) and simulated acid rain on whole plant net photosynthetic rate were observed, but not on other determined parameters. The exposure of the seedlings to O(3) caused the reductions in the dry weight growth, root dry weight relative to the whole plant dry weight, net photosynthetic rate, transpiration rate in light, water-use efficiency and root respiration activity, and increases in shoot/root ratio, and leaf dry weight relative to the whole plant dry weight without an appearance of acute visible foliar injury, but did not affect the dark respiration rate and transpiration rate in the darkness. The decreased net photosynthetic rate was considered to be the major cause for the growth reduction of the seedlings exposed to O(3). On the other hand, the exposure of the seedlings to simulated acid rain reduced the net photosynthetic rate per unit chlorophyll a + b content, but did not induce the significant change in other determined parameters.

Journal Article↗
PubMed1996

Long-term expression of the 35,000 mol. wt fos-related antigen in rat brain after kainic acid treatment.

Systemic injection of kainic acid, a rigid analogue of glutamate, induces both the short-term and the long-term expression of activator protein-1 transcription factors. The short-term responses of activator protein-1 factors such as c-fos and fos-related antigens have been well studied. However, the long-term expression of activator protein-1 factor(s) induced by kainic acid is poorly understood. The present study was designed to document the long-term expression (up to seven months) of the fos-related antigens and to map their distributions in the rat brain after systemic treatment with kainic acid. A single dose of kainic acid (8 mg/kg) was injected i.p. into Fischer 344 rats and their epileptic seizure behaviour was monitored. The rats with full limbic seizures were chosen for long-term study. By using immunocytochemistry with an antibody that cross-reacts with all known fos-related antigens, western blot analysis and a gel mobility-shift assay, we have now shown that a 35,000 mol. wt fos-related antigen was induced by kainic acid treatment and expressed at high levels for up to five months. This fos-related antigen still maintains the activator protein-1 DNA binding activity in the rat brain seven months after kainic acid treatment. The fos-related antigens and activator protein-1 binding activity were continuously expressed at high levels throughout the experimental period in the dentate granule cells where mossy fibre collateral sprouting occurred after kainic acid treatment. Our results suggested that long-term expression of fos-related antigen may reflect the pathophysiological changes after kainic acid administration.

Animals↗
PubMed1996

The Women's Health Trial Feasibility Study in Minority Populations: design and baseline descriptions.

The Women's Health Trial: Feasibility Study in Minority Populations (WHT:FSMP), a randomized trial of 2208 women, was conducted to investigate three questions. First, can women from minority and low-socioeconomic-status populations be recruited in numbers sufficient to evaluate a dietary intervention designed to lower fat intake. Second, the efficacy of a low fat, increased fruit/vegetable/ grain product intervention for reducing fat consumption. Third, will participation in the intervention lower plasma cholesterol and estradiol levels relative to the controls. The baseline results showed that an adequate number of minority and low SES women could be recruited to test the study hypotheses. A diverse study population of postmenopausal women consuming a high fat diet was recruited: 28% of participants were Black, 16% were Hispanic, 11% had less than a high school level of education, and 15.5% had household incomes of < $15,000.

Aged↗
PubMed1996

The accuracy of computed tomography-based linear measurements of human femora and titanium stem.

RATIONALE AND OBJECTIVES: The authors investigate the accuracy of computed tomography linear measurement of femora with titanium stem, and the effect of the stem on these measurements. MATERIALS AND METHODS: Two embedded cadaveric femora, one of them containing a titanium stem, and two cortical bone parallelepipeds were scanned. Thirty-six cross-sections were studied, each measured in two linear directions by the profile window technique. A half-maximum height method was used to determine the cortex-gap-titanium sizes from the computed tomography (CT) images. The accuracy of the measurements from the parallelepipeds, femora, and titanium stem taken from the CT was compared with those taken by a digital caliper of anatomical sections at the same level of the same bone. RESULTS: Computed tomography measurements of the parallelepipeds were similar to the anatomical size (mean relative error 0.04% +/- 0.63%). The mean error and mean relative error of the cadaveric femora CT with and without the stem were similar to the control parallelepipeds. Higher values of error were found for the titanium stem. CONCLUSIONS: The half-maximum height method in the profile window provides an accurate measurement of the femoral cortex and the titanium stem. The presence of the titanium stem in the medullary cavity of the femur did not interfere with the measurements of cortical dimensions.

Aged↗
PubMed1996

Stimulation of human lymphocyte proliferation and CD40 antigen expression by phosphorothioate oligonucleotides complementary to hepatitis B virus genome.

We have studied the proliferation and CD40 antigen expression of lymphocytes, and the cytotoxicity to monocytes, of antisense phosphorothioate oligodeoxynucleotides complementary to the SP II promoter of HBV mRNA (sequence I) and the X gene (sequence II) in patients with chronic hepatitis B. The oligo sequence I stimulated proliferation of both T and, to a lesser extent, B cells. The percentage of cells expressing CD40 in T and B cell co-cultures increased from 4.2% to 13.8% after oligo stimulation in patients, while it increased form 4.7% to 48.6% in healthy controls. The sense sequence (sequence III) of the X gene also enhanced the expression of CD40 antigen in patients with hepatitis B. The proportion of CD40 cells (26%) in a resting B-cell preparation from hepatitis B patients decreased to zero after a 5-day culture with sequence I, but IgG levels in the culture supernatant increased. The cytotoxic properties of monocytes were not influenced by the oligos. These findings indicate that antisense oligos against hepatitis B virus (HBV) have mitogenic effects on the proliferation of human lymphocytes in a non-specific manner and may activate T cells to express CD40 antigen.

Adult↗