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Biomedical subjects

W Fang

Publications and source records attributed to W Fang.

At least 91 records · Page 5Linked to original sources
PubMed1996

Frequent aberrant immunoglobulin gene rearrangements in pro-B cells revealed by a bcl-xL transgene.

During B lymphocyte development, pro-B cells that fail to rearrange an immunoglobulin heavy (IgH) chain allele productively are thought to undergo developmental arrest and death, but because these cells are short-lived in vivo they are not well characterized. Transgenic mice expressing the apoptosis regulatory gene bcl-xL in the B lineage developed large expansions of pro-B cells in bone marrow. V(D)J rearrangements in the expanded populations were nearly all nonproductive, and DJH rearrangements were enriched for joints in DH reading frame 2 and for aberrant joints with extensive DH or JH deletions. Thus, the death of pro-B cells with failed immunoglobulin rearrangements occurs by apoptosis, and bcl-xL can deliver a strong survival signal at the pro-B stage. This analysis also demonstrated that immunoglobulin gene rearrangement is less precise than previously appreciated.

Animals↗
PubMed1996

Quantification of Staphylococcus aureus and Escherichia coli in the liquid medium by fluorimetry and its use in phagocytosis assay.

A fluorimetric technique was compared with the plate counting method for quantification of viable cells of Staphylococcus aureus and Escherichia coli in the liquid medium. The fluorimetric assay measures the release of fluorogenic 4-methylumbelliferone (4-MU) from 4-methylumbelliferyl phosphate by the bacterial phosphatases. The increase in fluorescence was dependent on the size of bacterial inocula. Setting the fluorescence threshold at the middle of the logarithmic growth phase resulted in good linear relationship between bacterial counts and fluorescence (r = 0.99 for both Staph. aureus and E. coli). There was also an excellent correlation between the fluorimetric assay and the plate counting method in quantifying viable bacteria in saline (r = 0.99). Both methods were further compared for evaluation of extracellular bacteria following phagocytosis. The fluorimetric technique, in general, gave a higher percentage of phagocytosis than the plate counting method with statistical significance for E. coli.

Animals↗
PubMed1996

Disposition of enrofloxacin (Baytril) into the udder after intravenous and intra-arterial injections into dairy cows.

Enrofloxacin (Baytril) was injected into arteries supplying the udder of dairy cows. The idea was to avoid primary distribution, metabolism and elimination and thus to deliver the drug to the target organ at higher concentration. Enrofloxacin injected into the abdominal aorta or the external iliac artery resulted in high initial enrofloxacin retention by the udder and high milk concentrations. Injection of enrofloxacin into the abdominal aorta resulted in 2.2 times higher milk peak concentration of the drug than intravenous injection into the jugular vein. Injection of the drug into one of the two external iliac arteries allowed drug concentrations of milk from the udder halves to be compared: when enrofloxacin was injected into the right external iliac artery, the peak milk enrofloxacin concentration from the right udder half was 4.8 times that of the left udder half. The bulk of enrofloxacin was absorbed from the milk compartment of the udder before the next regular milking 6.5 h later. By this time, the metabolite ciprofloxacin had accumulated in milk. Pharmacokinetic values for enrofloxacin and its metabolite ciprofloxacin are given separately for serum and milk whey following three intravascular dosing routes.

Animals↗
PubMed1996

Mastitis-causing Escherichia coli: serum sensitivity and susceptibility to selected antibacterials in milk.

A total of 169 Escherichia coli strains were isolated from cows with cases of clinical mastitis. beta-Glucuronidase production, serum sensitivity, and susceptibility to selected antibacterials were analyzed using the fluorometric beta-glucuronidase assay. About 89% (150 of 169) of the isolates tested positive for beta-glucuronidase. Of these isolates producing beta-glucuronidase, 102 (68%) were resistant or moderately resistant to bovine serum. The antibacterial susceptibility of 96 isolates was tested in broth and milk. There was a significant shift from lower fluorometric minimum inhibitory concentration for tetracycline, sulfadoxin-trimethoprim, enrofloxacin, and gentamicin in broth to higher fluorometric minimum inhibitory concentration in milk. Serum sensitivity and susceptibility to tested antibacterials in broth or in milk were not related. Gentamicin and sulfadoxin-trimethoprim seemed to be more potent in mastitic milk than in normal milk, suggesting a possible synergistic effect between these exogenous antibacterials and the indigenous antibacterial agents in mastitic milk.

Ampicillin↗
PubMed1996

Antagonism of lactic acid bacteria towards Staphylococcus aureus and Escherichia coli on agar plates and in milk.

The antagonistic effect of lactic acid bacteria (LAB, including Lactobacillus acidophilus, L. bulgaricus, L. casei and Streptococcus thermophilus) on Staphylococcus aureus and Escherichia coli was evaluated on MRS agar with the deferred and cross-streaking techniques, and in milk with the plate counting method. All LAB were repressive to S aureus and E coli on the agar medium. However, their suppressive activity was significantly reduced when the agar medium was buffered to pH 7.2. In normal milk, L acidophilus strains A and B, S thermophilus and its combinations with L acidophilus A and L bulgaricus 6032 were inhibitory to S aureus, while in mastitic milk, only S thermophilus and its combinations showed inhibition. L acidophilus A and L bulgaricus 34104 were repressive to E coli growth in normal milk. S thermophilus and its combinations were inhibitory to E coli in both the normal and mastitic milk samples. These results indicate that the antagonistic activity of LAB on pathogenic bacteria varied with the type of media in which the tests were done, and that testing of in vitro antagonism in milk would be more informative than that in artificial media for in vivo tests concerning the possible roles of competitive microbiological ecology in mastitis control.

Agar↗
PubMed1996

Reconstitution of mastitic milk by adding blood plasma and leukocytes into low cell count milk.

Milk from inflamed quarters is high in somatic cells, proteolytic activity and lysosomal enzyme activity. Addition of homologous blood plasma and leukocytes into low cell count milk did not increase the plasmin activity, total proteolytic activity or N-acetyl-beta-D-glucosaminidase (NAGase) as anticipated, even if the reconstituted milk samples were stimulated by endotoxin or opsonized zymosan. Addition of urokinase activated the latent proteolytic system in plasma-supplemented milk. The reactive sulfhydryls in milk samples with different treatments decreased significantly after incubation, indicating the presence of an oxidative mechanism in milk (eg, sulfhydryl oxidase). The high background resazurin reduction of fresh milk might be due, in part, to the cellular activity of somatic cells. This study indicates that a more complex system including inflammatory mediators and complex cellular interactions is required for expression of plasmin-activator activity and for full activation of the proteolytic and lysosomal enzymes in mastitic milk.

Acetylglucosaminidase↗
PubMed1996

Inhibition of the protease activity in tracheobronchial aspirates of horses with chronic obstructive pulmonary disease.

OBJECTIVES: To clarify the role of proteolytic enzymes in the pathogenesis of chronic obstructive pulmonary disease (COPD) in horses, and to investigate new possibilities for treatment of this disease by interfering in the proteolytic process. DESIGN: Effect of antiproteolytic activity of selected protease inhibitors on tracheal aspirates was studied in vitro, and the inhibition profiles were compared with those of purified proteases. SAMPLE POPULATION: Respiratory tract secretions with antiproteolytic activity from 9 horses with COPD. PROCEDURE: Caseinolytic agar-diffusion assay. RESULTS: The protease-inhibition profile of tracheal aspirates differed from horse to horse. The profiles did not resemble that of any of the pure proteases. Acetylcysteine, pentamidine, and diminazene were most effective in inhibiting proteolytic activity in tracheal aspirates in vitro. CONCLUSIONS: A mixed type of proteolytic activity is present in the respiratory tract secretions of horses with COPD. CLINICAL RELEVANCE: Acetylcysteine, pentamidine, and diminazene seem to have potential to be used in vivo to protect the lungs of horses with COPD from proteolytic damage.

Acetylcysteine↗
PubMed1996

Reduced tumorigenicity of metastatic human lung cancer cell subline (PGCL3) transfected with hRAR beta gene.

The recombinant PSG5-RAR beta plasmid and the G418-resistant PSV2 neo plasmid (10.1) were cotransfected into PGCL3 cells by coprecipitation with calcium phosphate. The transfectants CR3 and CR4, which expressed the RAR beta gene, were identified by Northern blot hybridization. The results showed that the in vitro growth and invasion of CR3 and CR4 were dramatically reduced compared to the control-transfected cell (CSV1). Furthermore, the colony-forming abilities in soft agar and the tumorigenicity in nude mice of CR3 and CR4 were abrogated. Our results suggests that RAR beta functions not only as a receptor mediating the RA action, but also as a suppressor in lung tumorigenesis.

3T3 Cells↗
PubMed1995

Bcl-xL rescues WEHI 231 B lymphocytes from oxidant-mediated death following diverse apoptotic stimuli.

Developing lymphocytes undergo extensive cell death during selection of the immune repertoire. We investigated the influence of bcl-xL, a member of the bcl-2 family of apoptosis regulatory genes, on apoptosis in a model system for negative selection in the B lymphoid lineage. Overexpression of bcl-xL in WEHI 231 immature mouse B cells blocked apoptosis triggered by cross-linking of surface IgM. bcl-xL-transfected cells were also resistant to apoptosis following incubation in low serum medium or exposure to gamma-irradiation, the sphingomyelin ceramide, or compounds that increase intracellular levels of oxidants. Remarkably, the addition of antioxidants (catalase, N-acetylcysteine, or pyruvate) alone rescued the native WEHI 231 cells from apoptosis while having only minor effects on the viability of cells overexpressing bcl-xL. Anti-IgM cross-linking, ceramide, and gamma-irradiation treatments elevated intracellular peroxide production, which was prevented by treatment with antioxidants. Cells overexpressing bcl-xL had a similar rise in intracellular oxidants as control cells, indicating that bcl-xL modifies the cell's response to oxidants while having no detectable influence on the endogenous production of oxidants following apoptotic stimuli. These data implicate bcl-xL as a potent death repressor in B lymphocytes and support the hypothesis that bcl-xL regulates survival decisions within susceptible cells by functioning downstream of oxidant production.

Animals↗
PubMed1995

A fluorometric beta-glucuronidase assay for analysis of bacterial growth in milk.

The growth of common mastitis-causing bacteria in milk was followed by a fluorometric technique based on the release of fluorescent 4-methylumbelliferone (4-MU) from 4-methylumbelliferyl-beta-D-glucuronide by the beta-glucuronidase of bacterial or milk origin. Three of four Escherichia coli strains, all four strains of Streptococcus uberis (4/4) and Streptococcus agalactiae (4/4) produced beta-glucuronidase. Four Staphylococcus aureus strains (4/4) and one E. coli strain, though unable to produce the enzyme, activated the milk beta-glucuronidase most probably by lowering the pH of bacterial cultures in milk for optimum activity of the indigenous enzyme. The beta-glucuronidase of milk, Str. uberis and Str. agalactiae origin had similar optimum pH ranges (5.3-6.6) while E. coli beta-glucuronidase was more active at neutral or slightly alkaline pH (6.8-7.7). The increase of beta-glucuronidase activity in milk cultures of E. coli, Str. uberis, Str. agalactiae and S. aureus seemed to parallel the increase of colony forming units and were dependent on the inoculum size. The time to reach a predetermined enzyme threshold in E. coli-milk cultures showed excellent linear relationship with the inoculum size.

Animals↗
PubMed1995

Inhibition of the proteinase activity in mastitic milk.

The antiproteolytic activity of selected proteinase inhibitors was studied in mastitic bovine milk and urokinase-activated normal milk using a caseolytic agar diffusion assay. The inhibition profiles of mastitic milk and urokinase-activated milk were compared with those of purified proteinases. The proteinase inhibition profile of mastitic milk did not resemble that of any of the pure proteinases, indicating a mixed type of proteinase system in mastitic milk. The trypanocidals diminazene (equivalent to Berenil) and pentamidine (equivalent to Lomidine), together with aprotinin (Trasylol), showed most promise when considering possible applications in mastitis to break up the proteolytic cascade within the inflamed udder.

Animals↗
PubMed1995

Potency of antibacterial drugs in milk as analysed by beta-glucuronidase-based fluorometry.

The potency of selected antibacterials on mastitis-causing Escherichia coli, Streptococcus agalactine and Streptococcus uberis in milk, whey and Iso-sensitest broth (ISB) was compared, based on the suppression of bacterial beta-glucuronidase production. The beta-glucuronidase activity in the samples was analysed by substrate-defined fluorometry where the turbidity of milk does not disturb the assay. In ISB, all four E. coli strains were susceptible to enrofloxacin and gentamicin, sulfadoxin-trimethoprim and tetracycline. S. agalactiae and S. uberis strains were susceptible in ISB to most of the antibacterials tested. The antibacterial potency of sulfadoxin-trimethoprim, tetracycline, novobiocin, gentamicin and enrofloxacin on E. coli and S. agalactiae were considerably decreased in milk as compared with that in ISB. However, S. uberis seemed to be more susceptible to antibacterials in milk or whey than in ISB. Regression analysis of the sigmoidal dose-response curves of sulfadoxin-trimethoprim showed that slopes of the linearized lines seemed to become less steep in milk than in the artificial broth medium, indicating a shift of the bactericidic effect in ISB towards a bacteriostatic effect in milk.

Animals↗
PubMed1995

Comparisons of selenite and selenium yeast feed supplements on Se-incorporation, mastitis and leucocyte function in Se-deficient dairy cows.

The dairy cows at the Estonian Agricultural University appeared to have an extremely low selenium status. The selenium level was 5.6 micrograms/l in whole blood and 3.2 micrograms/l in milk, on average. The blood glutathione peroxidase was consequently extremely low. The effects of organic selenium (selenized yeast) and sodium selenite were compared in a feeding experiment on 100 dairy cows. Selenium incorporation, udder health and the in vitro function of blood neutrophils were monitored. Supplementation of the feed either with 0.2 ppm organic selenium or sodium selenite for 8 weeks, increased the blood selenium level (geometric mean) within this period from the back-ground level (about 5.6 micrograms/l) to 167 (Se-yeast) and to 91 micrograms/l (selenite). The respective change in whole blood glutathione peroxidase (GSH-PX) was from 0.22 to 3.0 (Se-yeast) and to 2.3 (selenite) microKat/g Hb. Blood GSH-PX continued to increase up to 10 weeks after the supplementation was stopped. The bioavailability of yeast selenium was superior to selenite: the relative bioavailability (selenite = 1) of yeast selenium was 1.4 if blood GSH-PX, 1.9 if blood selenium, and 2.7 if milk selenium was used as the response criterion. Selenium-supplementation showed a positive effect on udder health. The percentage of quarters harbouring mastitis pathogens dropped from 22.9 to 13.0 in the Se-yeast group and from 18.4 to 7.4 in the selenite group during the supplementation period. The effect of selenium on mastitis was also reflected as a decrease in the output of milk somatic cells and N-acetyl-beta-D-glucosaminidase (NAGase). The time-luminescence profile of zymosan-induced activity of blood neutrophils became skewed to the left in Se-supplemented cows.

Acetylglucosaminidase↗
PubMed1995

Hypertension prevalence and status of awareness, treatment and control in China.

A nation-wide survey of blood pressure (BP) and high BP was made in China in 1991, using standardized methods and covering 950,356 men and women aged 15 years and above, from 30 provinces, autonomous regions, and municipalities. The purpose of the study was to estimate the prevalence and the status of awareness, treatment, and control of hypertension. The overall prevalence rate of hypertension defined as systolic BP > or = 140 or diastolic BP > or = 90 mmHg or currently on antihypertensive medication was 13.6%, and was higher in urban (16.3%) than in rural (11.1%) setting. The rate was 6.6% if a BP cut-point of 160/95 mmHg was used. Rates were low in younger age-groups but rose sharply after age 45. The total number of hypertensives in 1990 was estimated to be close to 90 millions. Of all hypertensives, about 1/4 were aware of their high BP, half of these were on medication, and only 3% had their BP controlled. All the rates were higher if the BP cut-point was 160/95 mmHg. Higher rates were found in urban than rural setting and, to a lesser degree, for women than men. In conclusion, hypertension was found to be common in China, and the rates of awareness, drug treatment, and controlled BP were low, indicating an urgent need for developing a national program of treatment and prevention of high BP.

Adolescent↗
PubMed1995

[Isolation and characterization of human lung cancer cell subline with different metastatic potential].

Single cell clones were isolated from metastatic human lung giant cell carcinoma (PG) using limited dilution method. After preliminary screening by in vitro invasion assay, tumorigenicity and spontaneous metastasis assay in nude mice, three cloned PG cell sublines (PGBE1, PGCL3 and PGLH7) were selected for further observation on morphology, chromosome number, in vitro growth and invasion assays, tumorigenicity and spontaneous metastasis to lung and lymph nodes in nude mice. We found that there was some difference on spontaneous metastasis to lung and lymph nodes in nude mice and in vitro invasive abilities between PGBE1 and PGLH7. But there were no obvious differences in other biological features among the three sublines. The results show that the PG cell line consists of different subpopulations of cells with different metastatic properties. These sublines may be valuable for further study on the molecular mechanisms of cancer metastasis.

Animals↗
PubMed1995

[Effects of site-selective 8-Cl-cAMP on the growth regulation of human lung giant cell cancer].

Type I and type II cAMP receptor proteins participate in cell growth regulation, differentiation and neoplastic transformation of neoplasms. In this paper the growth regulatory effects of cAMP analogs, DBcAMP (non-site-selective) and 8-Cl-cAMP (site-selective) on a highly metastatic human lung cancer cell line PG were studied. By MTT assay, DBcAMP at 1mmol/L was found to inhibit PG growth by 30% on the day 8, while 8-CL-cAMP at 10-20 mumol/L inhibited the growth by 75%-80%. When phosphodiesterase inhibitor isobutyl-1-methyl-xanthine (IBMX) was added the inhibitory effect of 8-Cl-cAMP was not enhanced, whereas that of DBcAMP was significantly enhanced. The invasiveness and colony-forming ability of the treated cells decreased. The cAMP level as determined by RIA was much more increased in DBcAMP-treated than in 8-Cl-cAMP-treated PG cells. The result suggests that 8-Cl-cAMP and DBcAMP exert their effects on tumor cell growth and invasion by defferent mechanisms.

8-Bromo Cyclic Adenosine Monophosphate↗