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Biomedical subjects

Z Feng

Publications and source records attributed to Z Feng.

At least 127 records · Page 7Linked to original sources
PubMed1999

Development of a transposon mutagenesis system for Mycobacterium avium subsp. paratuberculosis.

Mycobacterium avium subspecies paratuberculosis, a slow-growing Mycobacterium, is the causative agent of Johne's disease. Although M. paratuberculosis is difficult to manipulate genetically, our laboratory has recently demonstrated the ability to introduce DNA into these bacteria by transformation and phage infection. In the current study we develop the first transposon mutagenesis system for M. paratuberculosis using the conditionally replicating mycobacteriophage phAE94 to introduce the mycobacterial transposon Tn5367. Southern blotting and sequence analysis demonstrated that the transposon insertion sites are distributed relatively randomly throughout the M. paratuberculosis genome. We constructed a comprehensive bank of 5620 insertion mutants using this transposon. The transposition frequency obtained using this delivery system was 1.0 x 10(-6) transposition events per recipient cell. Auxotrophic mutants were observed in this library at a frequency of 0.3%.

Base Sequence↗
PubMed1999

Long-term increase of Sp-1 transcription factors in the hippocampus after kainic acid treatment.

Systemic administration of kainic acid (KA), a glutamate receptor agonist, causes robust seizures and has been used as an excellent rodent model for human temporal lobe epilepsy. Recently, we have demonstrated that a single injection of KA increases the steady-state levels of proenkephalin (PENK) mRNA in the rat hippocampus for at least one year. However, the molecular mechanisms underlying this long-term increase in PENK mRNA levels have not been clearly defined. To determine the possible involvement of the Sp-1 transcription factors in this regulation, electrophoresis mobility-shift assays were used to study the expression of Sp-1 factors in the hippocampus after KA treatment. The results showed that there are long-lasting increases in Sp-1 DNA-binding activity. The Sp-1 DNA-binding complexes were only competed by the non-radioactive Sp-1 element and not by ENKCRE2, AP-1 or CRE elements, indicating the specificity of Sp-1 DNA-binding activity. Since the expression of Sp-1 parallels the time course of long-lasting increase in the expression of PENK mRNA and mossy fiber sprouting after KA treatment, we hypothesize that the increase in Sp-1 activity may be associated with the long-term changes in the plasticity of hippocampal function after KA-induced seizures.

Animals↗
PubMed1999

Heightened transcription for enzymes involved in norepinephrine biosynthesis in the rat locus coeruleus by immobilization stress.

BACKGROUND: The locus coeruleus (LC), a target for CRH neurons, is critically involved in responses to stress. Various physiological stresses increase norepinephrine turnover, tyrosine hydroxylase (TH) enzymatic activity, protein and mRNA levels in LC cell bodies and terminals; however, the effect of stress on other enzymes involved in norepinephrine biosynthesis in the LC is unknown. METHODS: Rats were exposed to single (2 hour) or repeated (2 hour daily) immobilization stress (IMO). Recombinant rat dopamine b-hydroxylase (DBH) cDNA was expressed in E. coli and used to generate antisera for immunohistochemistry and immunoblots in LC. Northern blots were used to assess changes in mRNA levels for TH, DBH, and GTP cyclohydrolase I (GTPCH) in the LC in response to the stress. Conditions were found to isolate nuclei from LC and to use them for run-on assays of transcription. RESULTS: Repeated stress elevated the DBH immunoreactive protein levels in LC. Parallel increases in TH, DBH and GTPCH mRNA levels of about 300% to 400% over control levels were observed with single IMO, and remained at similar levels after repeated IMO. This effect was transcriptionally mediated, and even 30 min of a single IMO significantly increased the relative rate of transcription. CONCLUSIONS: This study is the first to reveal transcriptional activation of the genes encoding catecholamine biosynthetic enzymes in the LC by stress. In addition to TH, changes in DBH and GTPCH gene expression may also contribute to the development of stress-triggered affective disorders.

Analysis of Variance↗
PubMed1999

Explaining community-level variance in group randomized trials.

Between-community variance or community-by-time variance is one of the key factors driving the cost of conducting group randomized trials, which are often very expensive. We investigated empirically whether between-community variance could be reduced by controlling individual- and/or community-level covariates and identified these covariates from four large community-based group randomized trials or surveys: the Working Well Trial; Kaiser Adolescent Survey; Kaiser Adults Survey; and the Eating Patterns Study. We found that adjusting for covariates will often substantially reduce the between-community variance component. Therefore investigators could block the communities according to these covariates, or adjust for these covariates to improve the power of community trials. We found that the community-by-time variance components are always near zero in these data sets, especially for the surveys where a cohort was followed over time. The covariate adjustment had less impact on reducing the community-by-time variance for the cohort samples than for the cross-sectional samples. This suggests that blocking may not be necessary for the design of the group randomized trials where the change from baseline is of primary interest. The Working Well Trial data were used to illustrate this point.

Adolescent↗
PubMed1999

Inhibitory effect of recombinant FN polypeptide CH50 on the metastasis and tumor growth.

The inhibition of CH50, a recombinant polypeptide of human fibronectin, on the formation of tumor metastases in vivo was studied by inoculation of melanoma B16/F1 cells by hypodermic or intraperitoneal injection, and the size and amount of tumor nodes after therapy were measured. In the treatment of hypodermic tumor, local injection of CH50 produced much better efficacy than distance injection of CH50 did. The inhibitory effect of CH50 on the growth of tumor reached 50%. In the treatment of peritoneal metastasis, the inhibition of CH50 on metastases smaller than 1 mm was above 80%, and above 50% on metastases larger than 1 mm. A better efficacy was achieved if CH50 was used in combination with hydroxycamptothecine (HCPT), a chemotherapeutic agent. CH50 displayed a strong inhibitory effect on the formation of small metastasis and growth of larger nodes of tumor, suggesting that CH50 plays a very important role in combined treatment of tumor therapy.

Fibronectins↗
PubMed1999

The construction of Schistosoma japonicum vaccine BCG-Sj26GST and its identification.

The expression of foreign gene, Schistosoma Japonicum 26 ku antigen (Sj26GST), in Bacillus Calmette-Guerin (BCG), Mycobacterium (M. smegmatis) and Escherichia coli (E. coli) were studied. The cDNA fragment encoding Sj26GST was amplified by PCR using plasmid pGEX, which could express Sj26GST in E. coli as template. The Sj26GST cDNA was cloned into the down-stream of human M. tuberculosis heat shock protein (hsp) 70 promoter with correct reading frame, and then the DNA fragment containing hsp70 promoter and Sj26GST gene were subcloned together into E. coli-Mycobacteria shuttle plasmid pBCG-2000 to construct the expression shuttle plasmid pBCG-Sj26. The recombinant BCG and M. smegmatis mc(2)155, which were electroplated with pBCG-Sj26, could express Sj26GST and the recombinant Schistosoma Japonicum vaccine BCG-Sj26GST was made. The recombinant Sj26GST (rSj26GST) were soluble and could be observed on SDS-PAGE at molecular weight of 26 ku. The content of rSj26GST accounted for 15% and 10% of total bacterial protein in BCG and M. smegmatis respectively. The results of Western blot showed the combination of rSj26GST with antibody of GST.

Animals↗
PubMed1999

Baseline fruit and vegetable intake among adults in seven 5 a day study centers located in diverse geographic areas.

OBJECTIVE: To examine baseline rates of fruit and vegetable consumption among adults in the 5 A Day research trials in order to identify any regional and sociodemographic differences associated with daily servings. DESIGN: The main outcome measure was the frequency of fruits and vegetables consumed within 1 month of the baseline survey as assessed by a 7-item food frequency questionnaire (FFQ). SUBJECTS/SETTING: Participants (N = 15,060) were from 7 study centers. Study centers included schools (N = 48), worksites (N = 60), churches (N = 50), or the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) clinics (N = 15) in interventions to increase fruit and vegetable consumption. STATISTICAL ANALYSES: Means and standard errors, adjusting for clusters, were calculated. A mixed linear model analyzed relationships between fruit and vegetable consumption and regional center, gender, age, race, education, income, marital status, food-shopping responsibility, and whether one lives with children. RESULTS: Results indicate an overall mean intake of 3.6 daily servings of fruits and vegetables. Significant differences in mean daily servings were found among the regional study centers (low of 3.0 to high of 4.1). There were significant differences in mean daily consumption by age (< 30 years = 3.7 servings per day; 30 to 49 years = 3.4; > or = 50 years = 3.7), education (> high school = 3.4 servings per day; high school graduate = 3.4; some college = 3.5; college graduate = 3.9), race (black = 3.7 servings per day; Hispanic = 3.0; white = 3.6; other = 3.7), marital status (married = 3.6 servings per day; single = 3.5), and food-shopping responsibilities (little = 3.2 servings per day; about half = 3.6; most = 3.8). Only 17% of respondents ate 5 or more servings of fruits and vegetables per day. CONCLUSIONS: The 7 regions showed significant variability in daily fruit and vegetable consumption, suggesting that a single national message to increase fruit and vegetable consumption may not reach the population segments most in need of changing. It is advisable to spend more time understanding the food consumption habits of the population under investigation to develop messages to foster behavior change.

Adolescent↗
PubMed1999

Microsurgical flaps for limb salvage in children.

We evaluated the results of microsurgical flaps for wound coverage in limb salvage cases at Arkansas Children's Hospital. Ages ranged from one to 18 years with a mean of 7.7 years. Sixteen children with soft tissue defect in 18 limbs were reconstructed with 19 free tissue transfer. Only one out of 19 free flaps failed, which necessitated a second free flap, giving an overall initial flap success rate of 95%. One flap developed superficial muscle necrosis, requiring debridement followed staged skin graft. All limbs were successfully salvaged. Our series confirms that microsurgical flap surgery is safe and effective in children, with limb salvage approaching 100 percent.

Adolescent↗
PubMed1999

A molecular perspective on the genera Paragonimus Braun, Euparagonimus Chen and Pagumogonimus Chen.

The status of the genera Euparagonimus Chen, 1963 and Pagumogonimus Chen, 1963 relative to Paragonimus Braun, 1899 was investigated using DNA sequences from the mitochondrial cytochrome c oxidase subunit I (CO1) gene (partial) and the nuclear ribosomal DNA second internal transcribed spacer (ITS2). In the phylogenetic trees constructed, the genus Pagumogonimus is clearly not monophyletic and therefore not a natural taxon. Indeed, the type species of Pagumogonimus, P. skrjabini from China, is very closely related to Paragonimus miyazakii from Japan. The status of Euparagonimus is less obvious. Euparagonimus cenocopiosus lies distant from other lungflukes included in the analysis. It can be placed as sister to Paragonimus in some analyses and falls within the genus in others. A recently published morphological study placed E. cenocopiosus within the genus Paragonimus and probably this is where it should remain.

Animals↗
PubMed1999

Effect of artemether on phosphorylase, lactate dehydrogenase, adenosine triphosphatase, and glucosephosphate dehydrogenase of Schistosoma japonicum harbored in mice.

AIM: To study the effect of artemether (Art) on phosphorylase (PP), lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-PDH), and adenosine triphosphatase (ATPase) of S japonicum. METHODS: Mice infected with S. japonicum cercariae for 32-38 d were treated i.g. with Art 100-300 mg.kg-1 and killed 24-72 h after treatment for collection of schistosomes. The activities of PP, LDH, and G-6-PDH were measured by the formation of NADH or NADPH. The activity of ATPase was measured by the rate of release of inorganic phosphate (Pi) from ATP at 37 degrees C. RESULTS: After infected mice were treated i.g. with Art 300 mg.kg-1 for 24-48 h, the activities of total PP and PPa (active form) increased markedly in both male and female worms, while PPb (inactive form) showed no or only a slight increase. At 24-72 h after the above-mentioned mice were treated i.g. with Art 100-300 mg.kg-1, the inhibitory rates of LDH and G-6-PDH were 9%-59% (male) and 41%-75% (female) as well as 22%-42% (male) and 74%-89% (female), respectively. When Art 300 mg.kg-1 was given to infected mice for 24 h, only the activity of Mg(2+)-ATPase showed marked inhibition in both male and female worms. At 48 h, the Ca(2+)-ATPase, Mg(2+)-ATPase, and Na(+)-K(+)-ATPase were all inhibited, the inhibitory rates of 17% (male) and 19% (female), 32% (male) and 48% (female) as well as 29% (male) and 44% (female), respectively. CONCLUSION: In schistosomes, the increase in the activity of AMP-independent PPa induced by Art may enhance the decomposition of glycogen and the inhibition of LDH by Art could reduce the formation of lactate. Moreover, Art exerts a potent inhibition on the G-6-PDH activity of the female S japonicum.

Adenosine Triphosphatases↗
PubMed1999

Enzyme-linked immunoelectrotransfer blotting analysis of human serologic responses to infective hookworm larval antigen.

OBJECTIVE: To explore the possibility of using specific antigens for immunodiagnosis of hookworm disease in endemic area. METHOD: Infective third-stage larvae of the canine hookworm, Ancylostoma caninum (A. caninum), were prepared as the source of antigen. Enzyme-linked immunoelectrotransfer blotting (EITB) was employed as an immunodiagnostic method. RESULTS: Two immunodominant bands of hookworm antigens (42 kDa and 55 kDa) were recognized by the sera of hookworm-infected patients (serum dilution 1:200; antigen centrifuged at 36,000 r/m for 20 minutes, but not by sera from negative controls. CONCLUSION: The 42 kDa and 55 kDa A. caninum antigens might be the specific antigens that could be used for immunodiagnosis of hookworm disease in endemic area.

Ancylostoma↗
PubMed1999

Length of protection by murine vaccination with living infective third-stage hookworm larvae.

OBJECTIVE: To determine the length of protection by murine immunization with living third-stage hookworm larvae (L3) as measured by reduction in worm burden and host serologic antibody responses. METHODS: Outbred male (Kunming strain) mice were immunized subcutaneously with 500 L3 once every 2 weeks for a total of immunization for 3 times, and then challenged orally with 1000 L3 for 1 to 8 weeks after the final immunization. Host protective immunity was determined both by the reduction in worm burden as measured by the number of L3 recovered from murine lungs 48-hour post-challenge, as well as by measurement of circulating antibodies. Histopathological responses were also examined. Non-immunized mice served as negative controls. RESULTS: The protection by L3 immunization declined over time. One or 2 weeks after the final immunization, worm burdens were reduced 72% and 77.5% after challenge respectively. In contrast, only 37% reduction in worm burden was observed when the L3 challenge was delayed by 4 weeks and protection was almost entirely lost when there was an 8 week delay between the time of final immunization and challenge. The reduced level of protection over time partially correlated with diminishing L3-specific antibody responses. Host inflammation in the lungs of immunized mice also diminished. CONCLUSION: The protection afforded by living L3 immunization is maximal for the first two weeks after immunization, but then declines significantly over the ensuing weeks.

Ancylostoma↗
PubMed1999

Cutaneous and subcutaneous mast cell and eosinophil responses after challenge in mice vaccinated with living infective third-stage hookworm larvae.

OBJECTIVE: To examine the quantitative and qualitative alterations in mast cells and eosinophils distributed in the cutaneous and subcutaneous tissues of hookworm-infected, uninfected and vaccinated mice. METHODS: Outbred male Kunming strain mice, weighing 18-22 g, were vaccinated thrice by subcutaneous inoculation with 500 living third-stage infective larvae (L3) of Ancylostoma caninum (A. caninum) every 2 weeks, and then challenged subcutaneously with 500 L3 one week after the final immunization. Uninfected mice and non-immunized mice but infected with L3 served as controls. The abdominal skin at the site of percutaneous entry was excised from challenged mice at intervals between 6 hours and 7 days after challenge, fixed, and then examined by light microscopy after staining with either toluidine blue or hematoxylin and eosin. RESULTS: The total number of mast cells appearing in cutaneous, and subcutaneous tissues, and underlying abdominal musculature of immunized mice increased significantly compared with non-immunized mice. Mast cells from hookworm-infected mice showed evidence of membrane rupture and degranulation in contrast to the intact appearance of mast cells from uninfected mice. The degree of mast cell degranulation was greater in vaccinated and challenged mice when compared with non-immunized and infected mice. Similarly, eosinophilic infiltration was greatly enhanced after L3 infection. Tissues from vaccinated mice had a greater number of eosinophils than non-immunized mice after infection. CONCLUSIONS: Mast cell alterations appearing earlier than tissue eosinophilic infiltration is major inflammatory response to Ancylostoma caninum (A. caninum) L3 infection in mice. These processes are more obvious in L3-vaccinated mice.

Ancylostoma↗
PubMed1999

[The inhibitory effect of recombinant fibronectin polypeptide CH50 on the growth of B16 melanoma].

OBJECTIVE: To study the inhibitory effect of CH50, a recombinant polypeptide consisting of 2 binding domains of human fibronectin, on the growth of B16/F1 melanoma in mice. METHODS: Mice inoculated with B16/F1 cells were treated with CH50. The growth inhibitory effect on i.p. inoculated tumor was assessed by the number and size of tumor nodules in the peritoneal cavity, and on s.c. inoculated tumor by tumor size. RESULTS: For s.c. inoculated B16/F1, CH50 injected at the tumor site led to 50% inhibition of tumor growth while injection at a distant site was much less effective. In mice bearing i.p. inoculated tumor, the growth inhibition by CH50 on tumor nodules < 1 mm in diameter was 80% and 50+% on those > 1 mm. Synergistic therapeutic effect was obtained when CH50 used in combination with hydroxycamptothecine (HCPT). CONCLUSION: CH50 is effective in the treatment of B16/F1 melanoma. The effect can be enhanced when used in combination with HCPT.

Animals↗
PubMed1999

[Immune responses to recombinant expression plasmid encoding hepatitis C virus core antigen].

OBJECTIVE: To study the feasibility of DNA immunization with recombinant expression plasmid containing hepatitis C virus (HCV) core gene against HCV infection. METHODS: The recombinant plasmid containing HCV C gene was constructed and expressed transiently by using lipofectamine in the mouse SP2/0 cells. After appraisal and purification, these plasmid and control DNA were directly injected intramuscularly into BALB/c mice, HCV C specific antibody in the sera was checked with ELISA. Proliferative responses of spleen cells from experimental and control mice were determined by (3)H thymidine incorporation and cytotoxicity T lymphocyte (CTL) activity was measured by standard 4-h (51)Cr release assays. RESULTS: All immunized mice developed anti-HCV core antibodies and this antibody was dose and immune number dependent. Lymphoproliferative responses for HCV core antigen were higher in immunized mice than in control mice (P < 0.05), stimulation indices (SI) were 2.42 - 6.10. CTLs might induce approximately 63.13% lysis of pcDNA HCV C transfected SP2/0 target cells. CONCLUSION: It is suggested that HCV C gene immunization is a promising method of vaccination against HCV infection.

Animals↗
PubMed1999

[Sequencing of cytochrome C oxidase 1 gene of Ancylostoma duodenale and Necator americanus].

AIM: To identify the genetic diversity between Ancylostoma duodenale and Necator americanus. METHODS: Mitochondrial cytochrome C oxidase subunit 1 (CO1) gene was amplified from genomic DNA of human hookworms collected from infected patients in Hejiang County, Sichuan Province, and the purified PCR products were directly sequenced by using Licor auto-sequencer. RESULTS: The PCR products were about 700 bp. Alignment of CO1 gene fragment sequences showed 89.7% similarity between Ancylostoma duodenale and Necator americanus, but still certain nucleotide variations (10.3%) existed. CONCLUSION: CO1 gene sequence can be used as a marker to identify the two species of human hookworms.

Amino Acid Sequence↗