Bactericidal activity of M protein conserved region antibodies against group A streptococcal isolates from the Northern Thai population

Background  

Most group A streptococcal (GAS) vaccine strategies have focused on the surface M protein, a major virulence factor of GAS. The amino-terminus of the M protein elicits antibodies, that are both opsonic and protective, but which are type specific. J14, a chimeric peptide that contains 14 amino acids from the M protein conserved C-region at the carboxy-terminus, offers the possibility of a vaccine which will elicit protective opsonic antibodies against multiple different GAS strains. In this study, we searched for J14 and J14-like sequences and the number of their repeats in the C-region of the M protein from GAS strains isolated from the Northern Thai population. Then, we examined the bactericidal activity of J14, J14.1, J14-R1 and J14-R2 antisera against multiple Thai GAS strains.     

Functional characterizations of residues Arg-158 and Tyr-170 of the mosquito-larvicidal Bacillus thuringiensis Cry4Ba

The insecticidal activity of Bacillus thuringiensis (Bt) Cry toxins involves toxin stabilization, oligomerization, passage across the peritrophic membrane (PM), binding to midgut receptors and pore-formation. The residues Arg-158 and Tyr-170 have been shown to be crucial for the toxicity of Bt Cry4Ba. We characterized the biological function of these residues. In mosquito larvae, the mutants R158A/E/Q (R158) could hardly penetrate the PM due to a significantly reduced ability to alter PM permeability; the mutant Y170A, however, could pass through the PM, but degraded in the space between the PM and the midgut epithelium. Further characterization by oligomerization demonstrated that Arg-158 mutants failed to form correctly sized high-molecular weight oligomers. This is the first report that Arg-158 plays a role in the formation of Cry4Ba oligomers, which are essential for toxin passage across the PM. Tyr-170, meanwhile, is involved in toxin stabilization in the toxic mechanism of Cry4Ba in mosquito larvae. [BMB Reports 2014; 47(10): 546-551]     

The systematics and population genetics of Opisthorchis viverrini sensu lato: implications in parasite epidemiology and bile duct cancer

Together with host and environmental factors, the systematics and population genetic variation of Opisthorchis viverrini may contribute to recorded local and regional differences in epidemiology and host morbidity in opisthorchiasis and cholangiocarcinoma (CCA). In this review, we address recent findings that O. viverrini comprises a species complex with varying degrees of population genetic variation which are associated with specific river wetland systems within Thailand as well as the Lao PDR. Having an accurate understanding of systematics is a prerequisite for a meaningful assessment of the population structure of each species within the O. viverrini complex in nature, as well as a better understanding of the magnitude of genetic variation that occurs within different species of hosts in its life cycle. Whether specific genotypes are related to habitat type(s) and/or specific intermediate host species are discussed based on current available data. Most importantly, we focus on whether there is a correlation between incidence of CCA and genotype(s) of O. viverrini. This will provide a solid basis for further comprehensive investigations of the role of genetic variation within each species of O. viverrini sensu lato in human epidemiology and genotype related morbidity as well as co-evolution of parasites with primary and secondary intermediate species of host.     

Use of Polyclonal Antibodies to Identify Mycoplasma-like organisms (MLOs) From the Sudan and from Thailand

Rabbit polyclonal antibodies prepared against faba bean phyllody MLO from the Sudan reacted with its homologous antigen and with extracts of Catharanthus roseus experimentally infected with the same or a related MLO from Crotalaria saltiana showing symptoms of phyllody disease, as well as with extracts of naturally MLO-infected C. saltiana growing in the field in the Sudan. The antibodies also reacted positively with extracts of C. roseus experimentally infected with Crotalaria juncea phyllody MLO and soybean phyllody MLO from Thailand. Polyclonal antibodies prepared against an MLO associated with witches' broom disease in C. juncea reacted positively in ELISA tests with homologous antigen extracts from naturally infected C. juncea as well as with extracts from experimentally infected C. roseus and with extracts prepared from Sesamum indicum plants with phyllody symptoms growing in Thailand. There was no reaction between these antibodies and extracts from C. roseus plants infected with the MLOs associated with C. juncea phyllody or with soybean phyllody. No cross reactions were observed among the antigens and antibodies of the two MLO groups by immunoflorescence, ELISA or western blotting. However, the molecular weight of the principal protein antigen, determined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting was the same for both types of MLO. Serologically-similar MLOs thus occur in the Sudan and in Thailand, where they are associated with phyllody symptoms in C. saltiana and faba bean and with C. juncea and soybean, respectively. A second, serologically distinct MLO group was also found infecting C. juncea and S. indicum in Thailand but MLOs from this group have not yet been identified in crops from the Sudan.     

Role of different habitats for the functional response of Crytorrhinus lividipennis (Hemiptera: Miridae) on Nilaparvata lugens (Hemiptera: Delphacidae)

The functional response of a predator, Cyrtorrhinus lividipennis, on the brown planthopper, Nilaparvata lugens, was investigated in two different experimental habitats: a piece of tiller in a petri dish (5.5?cm in diameter) and a rice plant in a net cage (5.5?cm diameter?×?43?cm height) for 24?h at room temperature. In the petri dish experiment, 2nd–5th instar nymphs, adult male, and female C. lividipennis were introduced in separate experiments to eggs of N. lugens at densities of five, 10, 20, 30, and 40 eggs per piece of rice. In the rice plant experiment, each C. lividipennis was introduced to a cage with a rice plant containing N. lugens eggs. After 24?h, the number of dead eggs and remaining eggs were counted and data fitted to three functional response models. Among the three types of functional responses, Type II best described the predator response to host densities in N. lugens in both experimental habitats, according to the logistic regression analysis value. The results showed that C. lividipennis was a more effective predator in the rice plant experiment compared to the disc experiment. Additionally, the searching efficiency and handling time parameters were different in the two different experimental habitats. This may cause errors when applying the functional response to biological control and predator–prey models. Different habitats and other environmental conditions from the experiment and natural rice field have to be considered.     

Cadmium Removal Potential from Contaminated Soil by Tagetes erecta L. and Panicum maximum: Influence of Soil pH

The potential for cadmium (Cd) removal from contaminated soil by two species—marigold (Tagetes erecta L.) and Guinea grass (Panicum maximum)—was investigated in pot culture experiments in a greenhouse in triplicate. The concentration of Cd was varied from 50 to 200 mg kg^?1 and the pH was varied from 5.0 to 7.5 to investigate the effect of pH on Cd uptake. The results showed that total biomass of Guinea grass was around nine and seven times higher than that of marigold for Cd treatments of 50 and 100 mg kg^?1 at pH 5.0, respectively. Total cadmium uptake at Cd treatments of 50 and 100 mg kg^?1 at pH 5.0 by Guinea grass was 19.28 ± 3.14 and 36.06 ± 4.28 mg kg^?1, respectively, and for marigold was 15.66 ± 4.17 and 20.38 ± 3.24 mg kg^?1, respectively. The total Cd uptake by Guinea grass was 1.23 and 1.77 higher than that of marigold at Cd treatments of 50 and 100 mg kg^?1, respectively, at pH 5.0 due to higher biomass. The maximum Cd uptake by marigold and Guinea grass occurred at pH 5.0 at Cd treatment of 100 mg kg^?1. The results clearly show that the two species behave very differently for Cd uptake. Guinea grass is easy to grow, drought tolerant and, due to its higher biomass, it can be used for remediation of Cd-contaminated soil.     

XANES Investigation of Dynamic Phase Transition in Olivine Cathode for Li‐Ion Batteries

Dynamic phase transformation in olivine LiFePO₄ involving formation of one or more intermediate or metastable phases is revealed by an in situ time‐resolved X‐ray absorption near edge structure (XANES) technique. The XANES spectra measured during relaxation immediately after the application of relatively high overpotentials, where metastable phases are expected, show a continuous shift of the Fe K‐edge toward higher energy. Surprisingly, the Fe K‐edge relaxes to higher energies after current interrupt regardless of whether the cell is being charged or discharged. This relaxation phenomenon is superimposed upon larger shifts in K‐edge due to changes in Fe^2+/Fe³⁺ ratio due to charging and discharging, and implies an intermediate phase of larger Fe? O bond length than any of the known crystalline phases. No intermediate crystalline phases are observed by X‐ray diffraction (XRD). A metastable amorphous phase formed during dynamic cycling and which structurally relaxes to the equilibrium crystalline phases over a time scale of about 10 min after cessation of charging/discharging current is consistent with the experimental observations.     

Population Genetic Structuring in Opisthorchis viverrini over Various Spatial Scales in Thailand and Lao PDR

Khon Kaen Province in northeast Thailand is known as a hot spot for opisthorchiasis in Southeast Asia. Preliminary allozyme and mitochondrial DNA haplotype data from within one endemic district in this Province (Ban Phai), indicated substantial genetic variability within Opisthorchis viverrini. Here, we used microsatellite DNA analyses to examine the genetic diversity and population structure of O. viverrini from four geographically close localities in Khon Kaen Province. Genotyping based on 12 microsatellite loci yielded a mean number of alleles per locus that ranged from 2.83 to 3.7 with an expected heterozygosity in Hardy–Weinberg equilibrium of 0.44–0.56. Assessment of population structure by pairwise F_ST analysis showed inter-population differentiation (P<0.05) which indicates population substructuring between these localities. Unique alleles were found in three of four localities with the highest number observed per locality being three. Our results highlight the existence of genetic diversity and population substructuring in O. viverrini over a small spatial scale which is similar to that found at a larger scale. This provides the basis for the investigation of the role of parasite genetic diversity and differentiation in transmission dynamics and control of O. viverrini.