Antibacterial activity of the crude extract of Chinese green tea (Camellia sinensis) on Listeria monocytogenes

The antibacterial activity of the methanol and aqueous extract of Camellia sinensis on Listeria monocytogenes were investigated using agar-gel diffusion, paper disk diffusion and microbroth dilution techniques. The results obtained showed that methanol and water extract exhibitedantibacterial activities against L. monocytogenes. The leaf extract produced inhibition zone ranging from 10.0 – 20.1 mm against the test bacteria. The methanol extracts of the test plant produces largerzones of inhibition against the bacteria than the water extract. The minimum inhibitory concentration (MIC) for the methanol and water leaf extract was 0.26 and 0.68 mg/ml, respectively

A broadly effective vaccine against porcine post-weaning diarrhea

Doctor of PhilosophyDepartment of Diagnostic Medicine/PathobiologyYing FangWeiping ZhangEnterotoxigenic Escherichia coli are the major causes of porcine post-weaning diarrhea (PWD). Currently, no licensed vaccines for ETEC exist. However, studying ETEC helps to better understand the role of these organelles in biology and pathogenesis, opens a new door to disease diagnosis, prevention and treatment, and enables development of effective vaccines. In Chapter 2, the study was focused on mapping the immuno-dominant or neutralizing epitopes from the adhesive subunit FedF of F18 fimbriae. Our data showed that seven immune-dominant epitopes were identified from FedF subunit. Epitope fusions induced anti-F18 antibodies in subcutaneously immunized mice. Moreover, antibodies derived from each fusion significantly blocked adherence of a F18-fimbrial E. coli bacteria to pig intestinal cell line IPEC-J2. While all seven epitopes exhibited neutralizing activity, results from this study identified FedF epitopes #3 (IPSSSGTLTCQAGT) and #7 (QPDATGSWYD) as the most effective for antibodies against F18 fimbrial adherence and suggested their future application in PWD vaccine development. In Chapter 3, we further identified B-cell immunodominant epitopes from K88 fimbrial major subunit (also adhesin) FaeG. We found that while all nine FaeG epitope fusions induced antibodies to K88 fimbria, anti-K88 IgG antibodies derived from epitopes #1 (MTGDFNGSVD), #2 (LNDLTNGGTK), #3 (GRTKEAFATP), #4 (ELRKPDGGTN), #5 (PMKNAGGTKVGAVKVN) and #8 (RENMEYTDGT) significantly inhibited adherence of K88-fimbrial bacteria to porcine intestinal cell line IPEC-J2, indicating the ability of these peptides to neutralize EPITOPES of K88 fimbrial major subunit FaeG and suggesting the future application of FaeG epitopes in ETEC vaccine development. In Chapter 4, a PWD multiepitope fusion antigen (PWD-MEFA) was constructed. Our data showed the expressed fimbriae-toxoid PWD MEFA protein, which was approximately 40 kDa, was verified in Western blot analysis using anti-FaeG, anti-K88epitope-fusion, anti-F18epitope-fusion, anti-CT, anti-STa, and anti-Stx2e antiserum, respectively. Mice SC immunized with PWD MEFA protein developed strong anti-K88, anti-F18, anti-LT and anti-STb IgG antibody responses, and moderate anti-Stx2e and anti-STa IgG responses. Moreover, mouse serum antibodies inhibited adherence of K88- and F18-fimbrial ETEC bacteria and neutralized LT, STa, STb and Stx2e enterotoxicity. Additionally, double mutant LT (dmLT, LT subscript(R192G/L211A)) adjuvant up-immunoregulated PWD MEFA anti-fimbriae and antitoxin antibody responses. These results indicated that this fimbriae-toxoid PWD MEFA induced broadly anti-fimbriae and anti-toxin antibodies, and suggested antigen candidacy for developing an effective vaccine against PWD. In Chapter 5, we optimized this MEFA to be expressed as a holotoxin-structured and GM1-binding protein in a live host strain to induce mucosal antibodies against ETEC adhesins and toxins. Our data showed that optimized PWD adhesin-toxoid MEFA formed a holotoxin structure and bound to GM1 receptor, and Salmonella Ty21a strain, as well as porcine field E. coli isolate G58 to produce the new adhesin-toxoid MEFA and secreted the protein outer-membrane. These results suggest that Ty21a or G58 host producing the GM1-binding adhesin-toxoid MEFA can potentially be an effective mucosal vaccine against PWD. In summary, this study investigated the immunodominate and neutralizing epitopes of F18 fimbrial adhesin subunit FedF and K88 fimbrial adhesin subunit FaeG, and also constructed and optimized a PWD fimbriae-toxoid MEFA inducing broadly effective protection against PWD-associated ETEC infection

Integral and Rxte/Asm Observations on Igr J17098-3628

To probe further the possible nature of the unidentified source IGR J17098-3628, we have carried out a detailed analysis of its long-term time variability as monitored by RXTE/ASM, and of its hard X-ray properties as observed by INTEGRAL. INTEGRAL has monitored this sky region over years and significantly detected IGR J17098-3628 only when the source was in this dubbed active state. In particular, at $\ge$ 20 keV, IBIS/ISGRI caught an outburst in March 2005, lasting for $\sim$5 days with detection significance of 73$\sigma$ (20-40 keV) and with the emission at $<$200 keV. The ASM observations reveal that the soft X-ray lightcurve shows a similar outburst to that detected by INTEGRAL, however the peak of the soft X-ray lightcurve either lags, or is preceded by, the hard X-ray ($>$20 keV) outburst by $\sim$2 days. This resembles the behavior of X-ray novae like XN 1124-683, hence it further suggests a LMXB nature for IGR J17098-3628. While the quality of the ASM data prevents us from drawing any definite conclusions, these discoveries are important clues that, coupled with future observations, will help to resolve the as yet unknown nature of IGR J17098-3628.Comment: 15 pages, 7 figure, accepted in PAS

A Study of Strain-Induced Phase Transformations in TiNi Alloy by Electric Resistance Method

It is generally recognized that the shape memory effect (SME) is associated the interaction of stress with thermoelastic martensitic transformation [1]. The phase transformations in TiNi alloy was reported to occur as three kinds of B2→R, B2→M, R→M phase transformations [2]. There are different views about premartensitic transformation in TiNi based alloys. Mwang et al [3] reported a transformation sequence in TiNiFe alloy that was the parent B2→Incommensurate I→Rhombohedra R→Martensite M. But many authors [2,4] reported that the premartensitic structure of TiNi alloy is rhombohedra. It is known that the electric resistance increase in the premartensitic transformation range was because of the R-phase taking affect. The electric resistance decrease below the temperature MS was because of the martensite occurence. It is not clear what occurred when the SME alloy is made a plastic deformation. Muang et al [5] was reported that in a TiNi alloy the new rhombohedral phase, perhaps, was induced by stress in the internal friction experiment. In this paper the phase transformation induced by the plastic deformation was studied by the electric resistance method