Gyo Jun

Plasmodium vivax malaria: status in the Republic of Korea following reemergence.

The annual incidence of Plasmodium vivax malaria that reemerged in the Republic of Korea (ROK) in 1993 increased annually, reaching 4,142 cases in 2000, decreased to 864 cases in 2004, and once again increased to reach more than 2,000 cases by 2007. Early after reemergence, more than two-thirds of the total annual cases were reported among military personnel. However, subsequently, the proportion of civilian cases increased consistently, reaching over 60% in 2006. P. vivax malaria has mainly occurred in the areas adjacent to the Demilitarized Zone, which strongly suggests that malaria situation in ROK has been directly influenced by infected mosquitoes originating from the Democratic Peoples Republic of Korea (DPRK). Besides the direct influence from DPRK, local transmission within ROK was also likely. P. vivax malaria in ROK exhibited a typical unstable pattern with a unimodal peak from June through September. Chemoprophylaxis with hydroxychloroquine (HCQ) and primaquine, which was expanded from approximately 16,000 soldiers in 1997 to 200,000 soldiers in 2005, contributed to the reduction in number of cases among military personnel. However, the efficacy of the mass chemoprophylaxis has been hampered by poor compliance. Since 2000, many prophylactic failure cases due to resistance to the HCQ prophylactic regimen have been reported and 2 cases of chloroquine (CQ)-resistant P. vivax were reported, representing the first-known cases of CQ-resistant P. vivax from a temperate region of Asia. Continuous surveillance and monitoring are warranted to prevent further expansion of CQ-resistant P. vivax in ROK.

Resurgence of Plasmodium vivax Malaria in the Republic of Korea during 2006-2007

Plasmodium vivax malaria, which re-emerged in the Republic of Korea (ROK) in 1993, had decreased since 2001. However, case numbers began to increase again in 2005. The number of cases rose 54.0% in 2006, but the rate of increase slowed down in 2007. Among the total of 4,206 cases of P. vivax malaria during 2006-2007, 756 cases (18.0%) were ROK military personnel, 891 cases (21.2%) were veterans, and 2,559 cases (60.8%) were civilians. The rapid increase during this period was mostly contributed by the western part of the malaria-risk areas that is under the influence of adjacent North Korea. Local transmission cases in ROK have also increased gradually and the transmission period seemingly became longer. Chemoprophylaxis in the military should be re-assessed in view of chloroquine-resistance. Continuous surveillance and monitoring are warranted to prevent further expansion of P. vivax malaria caused by climate change in ROK.

Status of Plasmodium vivax malaria in the Republic of Korea, 2008–2009: decrease followed by resurgence

The number of Plasmodium vivax malaria cases in the Republic of Korea (ROK) in 2008 was 1009, a 54.2% decrease on the previous year. It then resurged to 1317 cases in 2009 (30.5% increase on 2008). One possible cause for the sharp decrease in 2008 might be the large-scale presumptive anti-relapse therapy with primaquine that was undertaken in the Democratic Peoples Republic of Korea in 2007. Of the 2326 cases of P. vivax malaria diagnosed in the ROK during 2008-2009, 599 cases (25.8%) were military personnel, 535 cases (23.0%) were veterans, and 1192 cases (51.2%) were civilians. Local transmission within the ROK appeared to increase gradually, and the length of the transmission period of P. vivax malaria extended during this period. Parasite clearance time after chloroquine treatment has increased in the late 2000s, which requires the introduction of countermeasures against the decreasing chloroquine susceptibility, including reduction of mass chemoprophylaxis with chloroquine in the ROK Army.

Telomerase and Apoptosis in the Placental Trophoblasts of Growth Discordant Twins

In an effort to investigate the molecular basis of growth discordance in embryos that experience the same uterine environment, we compared telomerase activity and apoptosis in placental trophoblasts obtained from growth discordant twins. Between January 2003 and February 2005, placental tissue from twenty pairs of twins was obtained within thirty minutes of delivery. Eleven cases were classified as growth discordant, with birth weight discordance greater than 20%. Nine cases comprised the control group, with less than 20% discordance. Telomerase and apoptotic activities in placental trophoblasts were analyzed by ELISA and immunoblot. Statistical significance was analyzed by a paired t-test, chisquared test, and ANOVA (SPSS ver 11.0). The average growth discordance was 26.8% in the growth discordant group and 14.4% in the control group. There were no significant differences in maternal age, week of gestation at delivery, parity, or chorionisity between the two groups. In the growth discordant group, the larger twin showed significantly higher telomerase activity (p < 0.01), whereas no significant difference was observed in the control group (p = 0.36). In addition, there was no definitive correlation between telomerase activity and the degree of growth discordance in the larger or smaller twins (R = -0.521 and -0.399, p = 0.15 and 0.25, respectively). The apoptosis proteins Bax and Bcl 2 were detected in both the larger and smaller twins in the growth discordant and control groups. There was no statistically significant difference in Bax expression between the larger and smaller twins (p = 0.25 and 0.92, respectively) for either the growth discordant or the control groups. Bcl 2 expression also showed no significant difference between groups. In conclusion, a tendency toward reduced telomerase activity and increased apoptosis was discovered in placental trophoblasts of the smaller growth-discordant twin, possibility resulting in delayed fetal growth.

Quantitative Determination of Plasmodium Parasitemia by Flow Cytometry and Microscopy

The traditional light microscopy has limitations for precise growth assays of malaria parasites in culture or for assessment of new compounds for antimalarial activity; the speed and high reproducibility of flow cytometry can overcome these limitations. A flow cytometric method using PicoGreen, a DNA-binding fluorochrome, was developed with optimal precision suitable for performing growth assays of low-parasitemia field isolates. In addition, intra- and inter-person reproducibility of the flow cytometric and the microscopic method were compared in order to quantitatively demonstrate the improved precision. RNase treatment contributed to the precision of the flow cytometric measurements by enhancing the signal-to-noise ratios. Coefficients of variation of the method were smaller than 10% for 0.1% or higher parasitemia samples. The intra- and inter-person coefficients of variation of the flow cytometric method were three to six times smaller than those of the microscopic method. The flow cytometric method developed in this study yielded substantially more precise results than the microscopic method, allowing determination of parasitemia levels of 0.1% or higher, with coefficients of variation smaller than 10%. Thus, the PicoGreen method could be a reliable high sensitivity assay for analysis of low parasitemia samples and might be applied to a high throughput system testing antimalarial drug activity.

Factors Affecting Reticulocyte Enrichment by Density Gradient Ultracentrifugation

cause cell volume changes, after clearly defining a criterion for fair comparison of the experimental conditions. After basal reticulocyte levels (BRLs) of 6 normal subjects were compared, the one with the highest BRL was selected as the blood donor (donor 1) during the initial phase of this study. However, we had to switch to another blood donor (donor 2) with the next high BRL because donor 1 had infections and received antibiotic therapy. This study was performed after written informed consents were obtained and the study protocol approved by the Institutional Review Board of Gil Medical Center, Gachon University of Medicine and Science. Since a control experiment revealed no difference between citrate/ dextrose anticoagulant (pH 7.4) and EDTA, Vacutainer TM tubes (BD, Franklin Lakes, N.J., USA) were used for blood collection. The BRL of donor 2 who provided blood samples for all the data presented here varied between 2.18 and 3.26% over the course of this study. Both donor 1 and donor 2 showed unusually high BRLs of 1 3% after they spent a stressful week with much less sleep than usual due to personal reasons. Presently, this is the only possible cause we can conjecture for the increased erythropoietic activity. Although repeated blood drawings can also induce erythropoiesis, this cause seems unlikely for our cases because the BRLs of both donors dropped to normal levels when they recovered from the severe tiredness despite regular blood donation. Reticulocytes constitute only 0.6–2.7% of the red blood cells (RBCs) in normal subjects [1] . Because of the low content, an efficient enrichment method is a prerequisite for studying the biology of reticulocytes. Several different types of enrichment methods have thus far been developed including density gradient centrifugation [2–7] , preparative electrophoresis [8] , affinity chromatography on transferrin-liganded sepharose [9] , as well as immunomagnetic separation using a monoclonal antibody to transferrin receptor [10] . Although almost pure reticulocytes can be obtained by the immunomagnetic method, density gradient ultracentrifugation still remains the method of choice when a large quantity of cells is required and a relatively low enrichment of 30–60% is acceptable. A strategy to maximize enrichment by density gradient ultracentrifugation can be developed based on the knowledge of cell volume control mechanisms such as regulatory cell volume decrease and regulatory cell volume increase [11–13] . A previous study utilized a high K +