Jae-Ran Yu

Rapid dissemination of newly introduced Plasmodium vivax genotypes in South Korea.

Reemerged Plasmodium vivax malaria in South Korea has not yet been eradicated despite continuous governmental efforts. It has rather become an endemic disease. Our study aimed to determine the genetic diversity in P. vivax merozoite surface protein-1 (PvMSP-1) and circumsporozoite protein (PvCSP) genes over an extended period after its reemergence to its current status. Sequence analysis of PvMSP-1 gene sequences from the 632 P. vivax isolates during 1996-2007 indicates that most isolates recently obtained were different from isolates obtained in the initial reemergence period. There was initially only one subtype (recombinant) present but its subtypes have varied since 2000; six MSP-1 subtypes were recently found. A similar variation was observed by CSP gene analysis; a new CSP subtype was found. Understanding genetic variation patterns of the parasite may help to analyze trends and assess extent of endemic malaria in South Korea.

Gymnophalloides seoi: a new human intestinal trematode

A new minute intestinal fluke, recovered from a Korean woman suffering from acute pancreatitis and gastrointestinal difficulties, was described as Gymnophalloides seoi. The coastal village where the patient resided was found to be a highly endemic area for this fluke, and 24 other endemic areas have been found. This fluke infection is now recognized as an emerging parasitic disease. Its second intermediate host is the oyster, and migrating birds are a natural definitive host. This new trematode might exist in other countries.

PYP-1, inorganic pyrophosphatase, is required for larval development and intestinal function in C. elegans

Inorganic pyrophosphatase (PPase) catalyzes the hydrolysis of inorganic pyrophosphate (PPi) into phosphate (Pi), which provides a thermodynamic driving force for important biosynthetic reactions. The nematode Caenorhabditis elegans gene C47E12.4 encodes a PPase (PYP‐1) which shows 54% amino acid identity with human PPase. PYP‐1 exhibits specific enzyme activity and is mainly expressed in the intestinal and nervous system. A null mutant of pyp‐1 reveals a developmental arrest at early larval stages and exhibits gross defects in intestinal morphology and function. The larval arrest phenotype was successfully rescued by reintroduction of the pyp‐1 gene, suggesting that PYP‐1 is required for larval development and intestinal function in C. elegans.

Prevalence of pediculosis capitis among Korean children

Pediculus humanus capitis is an ectoparasite, which causes scalp pruritus particularly among children. A total of 15,373 children including 8,018 boys and 7,355 girls from 26 primary schools and 15 kindergartens attached to the primary schools and a total of 33 children from an orphanage were examined for head lice infestation (HLI). The overall prevalence of HLI in this study was 4.1% including 3.7% of the urban areas and 4.7% of the rural areas. Head lice were found more frequently in girls than in boys with prevalence of 6.5% and 1.9%, respectively. The infestation rate by school grade was 3.2%, 4.7%, 4.2%, 5.0%, 4.9%, 3.8%, and 2.1% for kindergarten, first, second, third, fourth, fifth, and sixth grades, respectively. The infestation rate of the children in an orphanage was 66.7%. The prevalence of HLI has decreased especially in the rural areas. However, HLI is a still health problem of kindergarteners and primary schoolchildren in Korea.

Vacuolar-type H+-ATPase E subunit is required for embryogenesis and yolk transfer in Caenorhabditis elegans.

Vacuolar H(+)-ATPases (V-ATPases) are ATP-dependent proton pumps localized at membranes of intracellular acidic organelles and plasma membranes of various cell types. By virtue of its regulation in acidification, V-ATPase is required for many intracellular processes such as receptor-mediated endocytosis and protein sorting. Here we report the molecular characterization of the E subunit of V-ATPase in Caenorhabditis elegans. This subunit is one of the most well conserved subunits sharing approximately 57% identity with the human homologue, ATP6E. Green fluorescent protein (GFP) and whole-mount immunostaining analyses showed that V-ATPase E subunit (vha-8) is abundantly expressed in the H-shaped excretory cell, consistent with the expression patterns observed for other V-ATPase subunits. Double-stranded RNAs (or RNAi) targeted to vha-8 resulted in embryonic and larval lethality for the first filial generation, indicating that vha-8 is essential during early developmental processes. In addition, accumulation of abnormal endomitotic oocytes and defects in receptor-mediated endocytosis were observed in parental animals. These findings suggest that multiple phenotypes caused by the disruption of pH homeostasis are due to the defective V-ATPase. In summary, vha-8 encoding the E subunit of V-ATPase in C. elegans is essential for embryogenesis and receptor-mediated endocytosis.

Multiplex PCR Detection of Waterborne Intestinal Protozoa: Microsporidia, Cyclospora, and Cryptosporidium

Recently, emerging waterborne protozoa, such as microsporidia, Cyclospora, and Cryptosporidium, have become a challenge to human health worldwide. Rapid, simple, and economical detection methods for these major waterborne protozoa in environmental and clinical samples are necessary to control infection and improve public health. In the present study, we developed a multiplex PCR test that is able to detect all these 3 major waterborne protozoa at the same time. Detection limits of the multiplex PCR method ranged from 101 to 102 oocysts or spores. The primers for microsporidia or Cryptosporidium used in this study can detect both Enterocytozoon bieneusi and Encephalitozoon intestinalis, or both Cryptosporidium hominis and Cryptosporidium parvum, respectively. Restriction enzyme digestion of PCR products with BsaBI or BsiEI makes it possible to distinguish the 2 species of microsporidia or Cryptosporidium, respectively. This simple, rapid, and cost-effective multiplex PCR method will be useful for detecting outbreaks or sporadic cases of waterborne protozoa infections.

Detection of Cryptosporidium parvum in Environmental Soil and Vegetables

Cryptosporidium parvum is a zoonotic protozoan parasite that causes cryptosporidial enteritis. Numerous outbreaks of cryptosporidiosis have been reported worldwide. Cryptosporidium is transmitted to hosts via consumption of contaminated water and food but also by direct contact with contaminated soil or infected hosts. The present study investigated farm soil collected from 34 locations along the western Korean peninsula and 24 vegetables purchased from local grocery markets in Seoul. The soil and vegetable samples were examined by real-time polymerase chain reaction (qPCR) to estimate the risk of infection. Eleven of 34 locations (32.4%) and 3 of 24 vegetable samples (12.5%) were contaminated with Cryptosporidium parvum, as confirmed by TaqI enzyme digestion of qPCR products and DNA sequencing. It is suggested that Cryptosporidium infection can be mediated via farm soil and vegetables. Therefore, it is necessary to reduce contamination of this organism in view of public health. Graphical Abstract

Functional importance of polymerization and localization of calsequestrin in C. elegans

Dual roles of calsequestrin (CSQ-1) being the Ca2+ donor and Ca2+ acceptor make it an excellent Ca2+-buffering protein within the sarcoplasmic reticulum (SR). We have isolated and characterized a calsequestrin (csq-1)-null mutant in Caenorhabditis elegans. To our surprise, this mutant csq-1(jh109) showed no gross defects in muscle development or function but, however, is highly sensitive to perturbation of Ca2+ homeostasis. By taking advantage of the viable null mutant, we investigated the domains of CSQ-1 that are important for polymerization and cellular localization, and required for its correct buffering functions. In transgenic animals rescued with various CSQ-1 constructs, the in vivo patterns of polymerization and localization of several mutated calsequestrins were observed to correlate with the structure-function relationship. Our results suggest that polymerization of CSQ-1 is essential but not sufficient for correct cellular localization and function of CSQ-1. In addition, direct interaction between CSQ-1 and the ryanodine receptor (RyR) was found for the first time, suggesting that the cellular localization of CSQ-1 in C. elegans is indeed modulated by RyR through a physical interaction.

VHA‐8, the E subunit of V‐ATPase, is essential for pH homeostasis and larval development in C. elegans

Vacuolar H+‐ATPase (V‐ATPase) is an ATP‐dependent proton pump, which transports protons across the membrane. It is a multi‐protein complex which is composed of at least 13 subunits. The Caenorhabditis elegans vha‐8 encodes the E subunit of V‐ATPase which is expressed in the hypodermis, intestine and H‐shaped excretory cells. VHA‐8 is necessary for proper intestinal function likely through its role in cellular acidification of intestinal cells. The null mutants of vha‐8 show a larval lethal phenotype indicating that vha‐8 is an essential gene for larval development in C. elegans. Interestingly, characteristics of necrotic cell death were observed in the hypodermis and intestine of the arrested larvae suggesting that pH homeostasis via the E subunit of V‐ATPase is required for the cell survival in C. elegans.

Risk Factors Associated with Head Louse Infestation in Korea

Head louse infestation (HLI) is one of the most frequently occurring parasitic diseases in children. This study was conducted to investigate the socioeconomic and personal factors influencing HLI in the Republic of Korea. A total of 2,210 questionnaires about various factors related to HLI were obtained from children in 17 primary schools throughout the country. The rate of HLI was significantly lower in children who lived together with mother or in a family where both parents worked. In addition, HLI was lower in children whose fathers or mothers were public officers or teachers. However, HLI was higher in children who had small families and washed their hair less often. Education levels of parents and the number of children in family were not significant. Improvement of socioeconomic factors and personal hygiene will be helpful for reducing HLI.