Physical wounding-assisted Agrobacterium-mediated transformation of juvenile cotyledons of a biodiesel-producing plant, Jatropha curcas L.

The non-edible plant Jatropha curcas L. is one of the most promising feedstock for sustainable biodiesel production as it is not a source of edible vegetable oils, produces high amounts of oil (approx. 30–60% in dry seeds) and does not require high-cost maintenance. However, as with other undomesticated crops, the cultivation of J. curcas presents several drawbacks, such as low productivity and susceptibility to pests. Hence, varietal improvement by genetic engineering is essential if J. curcas is to become a viable alternative source of biodiesel. There is to date no well-established and efficient transformation system for J. curcas. In this study, we tested various physical wounding treatments, such as sonication and sand-vortexing, with the aim of developing an efficient Agrobacterium-mediated transformation for J. curcas. The highest stable transformation rate (53%) was achieved when explants were subjected to 1 min of sonication followed by 9 min of shaking in Agrobacterium suspension. The transformation frequency achieved using this protocol is the highest yet reported for J. curcas.     

Bioassay‐Guided Fractionation,Chemical Compositions and Antibacterial Activity of Extracts from Rhizomes of Globba schomburgkii Hook.f.

Bioassay‐guided fractionation was conducted on dichloromethane extract from the rhizomes of Globba schomburgkii Hook.f., which have previously been reported as the part with the highest antibacterial activity. 10 fractions and 20 sub‐fractions were obtained and evaluated for their potency against various strains of bacteria. The most active sub‐fractions were 8 times more effective against Staphylococcus aureus and Micrococcus luteus than the original crude extract. Moreover, two pure compounds, namely petasol and (E)‐15,16‐dinorlabda‐8(17),11‐dien‐13‐one, were successfully isolated and characterized for the first time from this plant species. Untargeted compound analysis of all fractions and sub‐fractions was performed by gas chromatography hyphenated with mass spectrometry, leading to positive identification of 167 compounds according to comparison with the mass spectrum and retention index database, 137 of which have never been reported for G. schomburgkii. The correlation between antibacterial activity and composition of each fraction suggests that the bioactive compounds could be 4,8‐β‐epoxycaryophyllene, methyl isocostate, (E)‐labda‐8(17),12‐diene‐15,16‐dial, α‐kessyl acetate, zederone, clovanediol, ledene oxide‐(I), alantolactone, or 8α,11‐elemadiol.     

Age or Stage Structure?

Discrete stage-structured density-dependent and discrete age-structured density-dependent population models are considered. Regarding the former, we prove that the model at hand is permanent (i.e., that the population will neither go extinct nor exhibit explosive oscillations) and given density dependent fecundity terms we also show that species with delayed semelparous life histories tend to be more stable than species which possess precocious semelparous life histories. Moreover, our findings together with results obtained from other stage-structured models seem to illustrate a fairly general ecological principle, namely that iteroparous species are more stable than semelparous species. Our analysis of various age-structured models does not necessarily support the conclusions above. In fact, species with precocious life histories now appear to possess better stability properties than species with delayed life histories, especially in the iteroparous case. We also show that there are dynamical outcomes from semelparous age-structured models which we are not able to capture in corresponding stage-structured cases. Finally, both age- and stage-structured population models may generate periodic dynamics of low period (either exact or approximate). The important prerequisite is to assume density-dependent survival probabilities.     

Proteomic analysis of chikungunya virus infected microgial cells

Chikungunya virus (CHIKV) is a recently re-emerged public health problem in many countries bordering the Indian Ocean and elsewhere. Chikungunya fever is a relatively self limiting febrile disease, but the consequences of chikungunya fever can include a long lasting, debilitating arthralgia, and occasional neurological involvement has been reported. Macrophages have been implicated as an important cell target of CHIKV with regards to both their role as an immune mediator, as well evidence pointing to long term viral persistence in these cells. Microglial cells are the resident brain macrophages, and so this study sought to define the proteomic changes in a human microglial cell line (CHME-5) in response to CHIKV infection. GeLC-MS/MS analysis of CHIKV infected and mock infected cells identified some 1455 individual proteins, of which 90 proteins, belonging to diverse cellular pathways, were significantly down regulated at a significance level of p<0.01. Analysis of the protein profile in response to infection did not support a global inhibition of either normal or IRES-mediated translation, but was consistent with the targeting of specific cellular pathways including those regulating innate antiviral mechanisms.     

Oleic acid Enhances Dengue Virus But Not Dengue Virus-Like Particle Production from Mammalian Cells

Despite the recent introduction of a commercial vaccine, the mosquito-transmitted dengue virus is still a worldwide public health problem. Based on the live attenuated vaccine strategy, the commercial vaccine has a less than optimal protective profile. Virus-like particles (VLPs) offer an attractive alternate vaccination strategy due to the effectively native presentation of epitopes in the absence of any infectious genetic material. However, the production of amounts of VLP in a platform that can support commercial development remains a major obstacle. This study generated two DENV 2 VLPs [codon-optimized and chimeric DENV/Japanese encephalitis virus (JEV)] and directly compared yields of these constructs by western blotting and dot blot hybridization. The effect of oleic acid supplementation, a process known to increase DENV production in natural infection, was also investigated. Results showed that the chimeric construct gave a two- to threefold higher yield than the codon-optimized construct and that while oleic acid increased DENV virion production in natural infection, it inhibited VLP production. These results suggest that further optimization of DENV VLP expression is possible, but it will require more understanding of how native DENV infection remodels the host cell machinery.     

From chaos to chaos. An analysis of a discrete age-structured prey–predator model

Discrete age-structured density-dependent one-population models and discrete age-structured density-dependent prey–predator models are considered. Regarding the former, we present formal proofs of the nature of bifurcations involved as well as presenting some new results about the dynamics in unstable and chaotic parameter regions. Regarding the latter, we show that increased predation may act both as a stabilizing and a destabilizing effect. Moreover, we find that possible periodic dynamics of low period, either exact or approximate, may not be generated by the predator, but it may be generated by the prey. Finally, what is most interesting from the biological point of view, is that given that the prey, in absence of the predator, exhibits periodic or almost periodic oscillations of low period, then the introduction of the predator does not alter this periodicity in any substantial way until the stabilizing effect of increased predation becomes so strong that a stable equilibrium is achieved. Received: 16 June 2000 / Revised version: 18 January 2001 / Published online: 12 October 2001     

Helicobacter pylori Infection in Thailand: A Nationwide Study of the CagA Phenotype

Background

The risk to develop gastric cancer in Thailand is relatively low among Asian countries. In addition, the age-standardized incidence rate (ASR) of gastric cancer in Thailand varies with geographical distribution; the ASR in the North region is 3.5 times higher than that in the South region. We hypothesized that the prevalence of H. pylori infection and diversity of CagA phenotype contributes to the variety of gastric cancer risk in various regions of Thailand.

Methods

We conducted a nationwide survey within Thailand. We determined H. pylori infection prevalence by detecting H. pylori, using histochemical and immunohistochemical methods. The anti-CagA antibody and anti-East-Asian type CagA antibody (α-EAS Ab), which showed high accuracy in several East Asian countries, were used to determine CagA phenotype.

Results

Among 1,546 patients from four regions, including 17 provinces, the overall prevalence of H. pylori infection was 45.9% (710/1,546). Mirroring the prevalence of H. pylori infection, histological scores were the lowest in the South region. Of the 710 H. pylori-positive patients, 93.2% (662) were immunoreactive with the anti-CagA antibody. CagA-negative strain prevalence in the South region was significantly higher than that in other regions (17.9%; 5/28; p < 0.05). Overall, only 77 patients (11.6%) were immunoreactive with the α-EAS Ab. There were no differences in the α-EAS Ab immunoreactive rate across geographical regions.

Conclusions

This is the first study using immunohistochemistry to confirm H. pylori infections across different regions in Thailand. The prevalence of East-Asian type CagA H. pylori in Thailand was low. The low incidence of gastric cancer in Thailand may be attributed to the low prevalence of precancerous lesions. The low incidence of gastric cancer in the South region might be associated with the lower prevalence of H. pylori infection, precancerous lesions, and CagA-positive H. pylori strains, compared with that in the other regions.