Estimating Geographical Variation in the Risk of Zoonotic Plasmodium knowlesi Infection in Countries Eliminating Malaria

BackgroundInfection by the simian malaria parasite, Plasmodium knowlesi, can lead to severe and fatal disease in humans, and is the most common cause of malaria in parts of Malaysia. Despite being a serious public health concern, the geographical distribution of P. knowlesi malaria risk is poorly understood because the parasite is often misidentified as one of the human malarias. Human cases have been confirmed in at least nine Southeast Asian countries, many of which are making progress towards eliminating the human malarias. Understanding the geographical distribution of P. knowlesi is important for identifying areas where malaria transmission will continue after the human malarias have been eliminated.Conclusions/SignificanceWe have produced the first map of P. knowlesi malaria risk, at a fine-scale resolution, to identify priority areas for surveillance based on regions with sparse data and high estimated risk. Our map provides an initial evidence base to better understand the spatial distribution of this disease and its potential wider contribution to malaria incidence. Considering malaria elimination goals, areas for prioritised surveillance are identified.     

Infection of less virulent Helicobacter pylori strains in asymptomatic healthy individuals in Thailand as a potential contributing factor to the Asian enigma

In Thailand, gastric cancer incidence is considerably low despite the high prevalence of Helicobacter pylori infection. We investigated the prevalence of H. pylori infection and the genotypes of cagA by using 179 stool specimens obtained from asymptomatic Thai individuals. In this study, the prevalence of H. pylori infection was 43.6%, and the detection rate of cagA-positive strains was 43.5%. In addition, the proportion of the highly virulent East-Asian type of cagA was 7.2%. These results indicate that the low prevalence of cagA-positive H. pylori strain as well as the low prevalence of East-Asian genotype cagA-positive strains may contribute to the low gastric cancer incidence.     

Design and synthesis of thiourea based receptor containing naphthalene as oxalate selective sensor

The thiourea based receptor containing naphthalene groups (1), has been successfully designed and synthesized for application as an oxalate receptor. A density functional theory at B3LYP/6-31G(d,p) level of theory has been applied to predict the binding ability between 1 and selected anions, i.e., oxalate, malonate, succinate, glutarate, dihydrogen phosphate, and hydrogen sulphate. Calculation results point out that receptor 1 shows the strongest interaction to oxalate ion with the binding free energy of 172.48 kcal mol⁻¹. The recognition ability of 1 to the selected anions has been also investigated by means of the absorption and emission techniques. Experimental results are in excellent agreement with the calculation data in which receptor 1 shows highly selective for oxalate ion over the other anions with logβ of 3.82 (0.02) M⁻¹ by means of the size of binding cavity.      

Genetic Diversity and Lack of Artemisinin Selection Signature on the Plasmodium falciparum ATP6 in the Greater Mekong Subregion

The recent detection of clinical Artemisinin (ART) resistance manifested as delayed parasite clearance in the Cambodia-Thailand border area raises a serious concern. The mechanism of ART resistance is not clear; but the P. falciparum sarco/endoplasmic reticulum Ca²⁺-ATPase (PfSERCA or PfATP6) has been speculated to be the target of ARTs and thus a potential marker for ART resistance. Here we amplified and sequenced pfatp6 gene (∼3.6 Kb) in 213 samples collected after 2005 from the Greater Mekong Subregion, where ART drugs have been used extensively in the past. A total of 24 single nucleotide polymorphisms (SNPs), including 8 newly found in this study and 13 nonsynonymous, were identified. However, these mutations were either uncommon or also present in other geographical regions with limited ART use. None of the mutations were suggestive of directional selection by ARTs. We further analyzed pfatp6 from a worldwide collection of 862 P. falciparum isolates in 19 populations from Asia, Africa, South America and Oceania, which include samples from regions prior to and after deployments ART drugs. A total of 71 SNPs were identified, resulting in 106 nucleotide haplotypes. Similarly, many of the mutations were continent-specific and present at frequencies below 5%. The most predominant and perhaps the ancestral haplotype occurred in 441 samples and was present in 16 populations from Asia, Africa, and Oceania. The 3D7 haplotype found in 54 samples was the second most common haplotype and present in nine populations from all four continents. Assessment of the selection strength on pfatp6 in the 19 parasite populations found that pfatp6 in most of these populations was under purifying selection with an average d_N/d_S ratio of 0.333. Molecular evolution analyses did not detect significant departures from neutrality in pfatp6 for most populations, challenging the suitability of this gene as a marker for monitoring ART resistance.     

Establishment of an Allo-Transplantable Hamster Cholangiocarcinoma Cell Line and Its Application for In Vivo Screening of Anti-Cancer Drugs

Opisthorchis viverrini (O. viverrini) is a well-known causative agent of cholangiocarcinoma (CCA) in humans. CCA is very resistant to chemotherapy and is frequently fatal. To understand the pathogenesis of CCA in humans, a rodent model was developed. However, the development of CCA in rodents is time-consuming and the xenograft-transplantation model of human CCA in immunodeficient mice is costly. Therefore, the establishment of an in vivo screening model for O. viverrini-associated CCA treatment was of interest. We developed a hamster CCA cell line, Ham-1, derived from the CCA tissue of O. viverrini-infected and N-nitrosodimethylamine-treated Syrian golden hamsters. Ham-1 has been maintained in Dulbecco''s Modified Essential Medium supplemented with 10% fetal bovine serum for more than 30 subcultures. These cells are mostly diploid (2n=44) with some being polyploid. Tumorigenic properties of Ham-1 were demonstrated by allograft transplantation in hamsters. The transplanted tissues were highly proliferative and exhibited a glandular-like structure retaining a bile duct marker, cytokeratin 19. The usefulness of this for in vivo model was demonstrated by berberine treatment, a traditional medicine that is active against various cancers. Growth inhibitory effects of berberine, mainly by an induction of G1 cell cycle arrest, were observed in vitro and in vivo. In summary, we developed the allo-transplantable hamster CCA cell line, which can be used for chemotherapeutic drug testing in vitro and in vivo.     

α-Tocopherol and lipid profiles in plasma and the expression of α-tocopherol-related molecules in the liver of Opisthorchis viverrini-infected hamsters

Opisthorchis viverrini infection induces inflammation-mediated oxidative stress and liver injury, which may alter α-tocopherol and lipid metabolism. We investigated plasma α-tocopherol and lipid profiles in hamsters infected with O. viverrini. Levels of α-tocopherol, cholesterol, and low-density lipoprotein increased in the acute phase of infection. In the chronic phase, α-tocopherol decreased, while triglyceride and very low-density lipoprotein increased. Notably, high-density lipoprotein decreased both in the acute and chronic phases. In the liver, cholesteryl oleate, triolein, and oleic acid decreased in the acute phase, and increased in the chronic phase. Such chronological changes were negatively correlated with the plasma α-tocopherol level. The expression of α-tocopherol-related molecules, ATP-binding cassette transporter A1 (ABCA1) and α-tocopherol transfer protein, increased throughout the experiment. These results suggest that O. viverrini infection profoundly affects on lipid and α-tocopherol metabolism in due course of infection.     

Ceftriaxone crystallization and its potential role in kidney stone formation

Drug-induced nephrolithiasis contributes to 1–2% of the incidence of renal calculi. We examined whether ceftriaxone at therapeutic doses could be crystallized in the urine and also explored its role in kidney stone formation. Crystallization was induced by mixing ceftriaxone sodium at therapeutic urinary excretion levels (0.5–4.0 mg/ml) to calcium chloride at physiologic urinary concentration (5 mM) in deionized (dI) water or artificial urine (AU). The results showed that ceftriaxone was crystallized with free calcium in dose- and time-dependent manner. These ceftriaxone/calcium crystals showed birefringence property under polarized microscope. Individual crystals had needle-shape (5–100 μm in length), whereas the aggregated form had star-burst and irregular-plate shape (40–200 μm in diameter) (note that the crystal sizes were much larger than renal tubular lumens). Calcium-depletion assay revealed that crystallization required free calcium as a substrate. In AU, crystallization remained although it was partially inhibited when compared to that in dI water. Finally, these crystals could tightly adhere onto renal tubular cell surface. Our data demonstrated that ceftriaxone at therapeutic levels could be crystallized with free calcium in the urine under physiologic condition. We hypothesize that tubular occlusion and crystal–cell adhesion may play important role in pathogenic mechanisms of ceftriaxone-induced nephrolithiasis.     

Limonoids from seeds of Thai Xylocarpus moluccensis

A new andirobin, thaimoluccensin A (1), and two new phragmalin-type limonoids, thaimoluccensins B (2) and C (3), were isolated from seeds of a Thai mangrove plant, Xylocarpus moluccensis, together with eight known compounds. The structures of these compounds were elucidated on the basis of spectroscopic data. Only 7-deacetylgedunin (7), a gedunin-type limonoid, exhibited significant inhibitory activity against nitric oxide production from activated macrophages with IC₅₀ value less than 10 μM, suggesting that the compound has anti-inflammatory activity.