Levels of genetic diversity of the malaria parasites and multiclonal infections are correlated with transmission intensity. In order to monitor the effect of strengthened malaria control efforts in recent years at the China-Myanmar border area, we followed the temporal dynamics of genetic diversity of three polymorphic antigenic markers msp1, msp2, and glurp in the Plasmodium falciparum populations. Despite reduced malaria prevalence in the region, parasite populations exhibited high levels of genetic diversity. Genotyping 258 clinical samples collected in four years detected a total of 22 PCR size alleles. Multiclonal infections were detected in 45.7% of the patient samples, giving a minimum multiplicity of infection of 1.41. The majority of alleles experienced significant temporal fluctuations through the years. Haplotype diversity based on the three-locus genotypes ranged from the lowest in 2009 at 0.33 to the highest in 2010 at 0.80. Sequencing of msp1 fragments from 36 random samples of five allele size groups detected 13 different sequences, revealing an additional layer of genetic complexity. This study suggests that despite reduced prevalence of malaria infections in this region, the parasite population size and transmission intensity remained high enough to allow effective genetic recombination of the parasites and continued maintenance of genetic diversity.

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Drug resistance has always been one of the most important impediments to global malaria control. Artemisinin resistance has recently been confirmed in the Greater Mekong Subregion (GMS) and efforts for surveillance and containment are intensified. To determine potential mechanisms of artemisinin resistance and monitor the emergence and spread of resistance in other regions of the GMS, we investigated the in vitro sensitivity of 51 culture-adapted parasite isolates from the China-Myanmar border area to four drugs. The 50% inhibitory concentrations (IC50s) of dihydroartemisinin, mefloquine and lumefantrine were clustered in a relatively narrow, 3- to 6-fold range, whereas the IC50 range of artesunate was 12-fold. We assessed the polymorphisms of candidate resistance genes pfcrt, pfmdr1, pfATP6, pfmdr6 and pfMT (a putative metabolite/drug transporter). The K76T mutation in pfcrt reached fixation in the study parasite population, whereas point mutations in pfmdr1 and pfATP6 had low levels of prevalence. In addition, pfmdr1 gene amplification was not detected. None of the mutations in pfmdr1 and pfATP6 was associated significantly with in vitro sensitivity to artemisinin derivatives. The ABC transporter gene pfmdr6 harbored two point mutations, two indels, and number variations in three simple repeats. Only the length variation in a microsatellite repeat appeared associated with altered sensitivity to dihydroartemisinin. The PfMT gene had two point mutations and one codon deletion; the I30N and N496– both reached high levels of prevalence. However, none of the SNPs or haplotypes in PfMT were correlated significantly with resistance to the four tested drugs. Compared with other parasite populations from the GMS, our studies revealed drastically different genotype and drug sensitivity profiles in parasites from the China-Myanmar border area, where artemisinins have been deployed extensively for over 30 years.

Plasmodium falciparum is usually asynchronous during in vitro culture. Highly synchronized cultures of Plasmodium falciparum are routinely used in malaria research. Here, we describe a simple synchronization procedure for P. falciparum asexual erythrocytic culture, which involves storage at 4°C for 8–24 h followed by routine culture. When cultures with 27–60% of ring stage were synchronized using this procedure, 70–93% ring stages were obtained after 48 h of culture and relative growth synchrony remained for at least two erythrocytic cycles. To test the suitability of this procedure for subsequent work, drug sensitivity assays were performed using four laboratory strains and four freshly adapted clinical P. falciparum isolates. Parasites synchronized by sorbitol treatment or refrigeration showed similar dose-response curves and comparable IC50 values to four antimalarial drugs. The refrigeration synchronization method is simple, inexpensive, time-saving, and should be especially useful when large numbers of P. falciparum culture are handled.

Compared with the vehicle in the sham group, ginsenoside had following effects. a) ginsenoside Rb1 increased the regional cerebral blood flow (rCBF) and the stability of neuronal ultrastructure in in the hippocampal CA1 region and improved the adaptability of neurons in two models. b) ginsenoside Rb1 improved the expression level of glial glutamate transporter1 (GLT-1) and reversed the uptake of glutamate (Glu) after ischemia, and as a result thereby decreased the excitability of Glu and the expression level of GLT-1 was proportional to the dose of ginsenoside Rb1 and similar to that of Nimodipine. c) ginsenoside Rb1 inhibited the expression level of NMDAR and the overload of Ca, thereby reducing neuronal damages. Meanwhile, the expression level of NMDAR was inversely proportional to the dose of ginsenoside Rb1, which was similar to that of Nimodipine. d) ginsenoside Rb1 decreased the release of cytochrome C (Cyt-C) and reduced the damages caused by neuronal mitochondrial stress. Meanwhile, the release of Cyt-C was inversely proportional to the dose of ginsenoside Rb1, which was similar to that of Nimodipine. Ginsenoside Rb1 may be as an effective drug for neuroprotection and improve cerebral blood flow after acute ischemia and prevent the secondary brain damage induced by stroke.

Antithrombotic effect of the copper-aspirin complex (dimeric copper(II) bis(o-acetoxybenzoate) was evaluated in the model of venous thrombosis; its effects on platelet-neutrophil adhesion were investigated by use of rosette assay. The results showed that the intragastrically administered copper-aspirin complex (5, 7, and 10 mg kg-1) dose-dependently lowered the wet and dry thrombus weight; it significantly decreased the binding of arachidonic acid-activated platelets to neutrophils with an IC50 value of 41.5 μmol L-1. The results suggested that copper aspirinate inhibited platelet-neutrophil adhesion and resulted in a more potent antithrombotic activity.

Effects of copper-aspirin complex on washed platelet aggregation, thromboxane B(2) formation and 6-ketoprostaglandin F(1alpha) level were monitored by Born's and Terashita's methods, respectively. The influence of copper-aspirin complex on cytosolic free calcium was examined using the fluorescent indicator, Fura 2-AM. Copper-aspirin complex significantly inhibited arachidonic acid-induced aggregation in washed platelets. The IC(50) value was 9.6 micromol L(-1). Copper-aspirin complex significantly decreased arachidonic acid-induced thromboxane B(2) formation by 87.1% in washed platelets. Ten mg kg(-1) of copper-aspirin complex given intragastrically markedly increased the plasma level of 6-keto-prostaglandin F(1alpha). Aspirin, however, reduced both thromboxane B(2) formation and 6-keto-prostaglandin F(1alpha) level. In the presence of CaCl2 1 mmol L(-1), copper-aspirin complex (20, 40 and 80 micromol L(-1)) markedly lowered arachidonic acid-induced increase in platelet calcium from the resting level (270+/-36 nmol L(-1)) to 213+/-14, 170+/-20 and 135+/-17 nmol L(-1), respectively. In the presence of ethylene glycol-bis (beta-aminoethyl ether) N,N,N',N'-tetraacetic acid 1 mmol L(-1), copper-aspirin complex (20, 40 and 80 micromol l L(-1)) significantly suppressed the release of intracellular calcium induced by arachidonic acid from 127+/-23 nmol L-1 to 108+/-17, 93+/-12 and 70+/-13 nmol L(-1).