Minchul Yoon

A MOVING MAT: PHOTOTAXIS IN THE FILAMENTOUS GREEN ALGAE SPIROGYRA (CHLOROPHYTA, ZYGNEMATACEAE)1

A blue light– (peak at 470 nm) induced photomovement was observed in the filamentous eukaryotic algae, Spirogyra spp. When Spirogyra filaments were scattered in a water chamber under a unilateral light source, they rapidly aligned toward the light source in 1 h and bound with neighboring filaments to form thicker parallel bundles of filaments. The filaments in the anterior of the bundles curved toward the light first and then those in the posterior began to roll up toward the light, forming an open‐hoop shape. The bundle of filaments then moved toward the light source by repeated rolling and stretching of filaments. When the moving bundle met other filaments, they joined and formed a bigger mat. The coordination of filaments was essential for the photomovement. The average speed of movement ranged between 7.8 and 13.2 μm·s−1. The movement was induced in irradiance level from 1 to 50 μmol photons·m−2·s−1. The filaments of Spirogyra showed random bending and stretching movement under red or far‐red light, but the bundles did not move toward the light source. There was no distinct diurnal rhythm in the photomovement of Spirogyra spp.

Possible surface carbohydrates involved in signaling during conjugation process in Zygnema cruciatum monitored with fluorescein isothiocyanate-lectins (Zygnemataceae, Chlorophyta)

The changes of cell surface carbohydrates were examined with FITC (fluorescein isothiocyanate)‐labeled lectins during the conjugation process of the green alga Zygnema cruciatum. The Ulex europaeus agglutinin (UEA)‐specific materials were detected consistently on the surface of vegetative cells, but were absent on the surface of protruding papillae or conjugation tube. The tips of male and female papillae were labeled with soybean agglutinin (SBA) and peanut agglutinin (PNA) during conjugation. The SBA‐ and PNA‐specific materials appeared first at the tip of male papillae and began to accumulate on the surface of female papillae. No labeling of these lectins was detected on the surface of vegetative filaments throughout the conjugation process. FITC‐ConA (Concanavalin A) and FITC‐RCA (Ricinus communis agglutinin) did not label the vegetative filaments of Z. cruciatum, but a trace labeling of these lectins was observed on the surface of some swollen papillae occasionally. Blocking experiments with various lectins showed that these SBA‐ and PNA‐specific glycoconjugates might be involved in the signaling between male and female papillae.

Anti-inflammatory effect of sweetfish-derived protein and its enzymatichydrolysate on LPS-induced RAW264.7 cells via inhibition of NF-κB transcription

The present study examined the anti-inflammatory effect of a sweetfish-derived protein and its hydrolysates on lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells. Hydrolysates of the sweetfish-derived protein were obtained on enzymatic hydrolysis by pepsin, trypsin, and α-chymotrypsin. The anti-inflammatory activity was determined based on the production of nitric oxide (NO), inflammatory cytokine [tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6)] and prostaglandin E2 (PGE2), mRNA expression levels of inflammation mediated proteins, and the inhibition of nuclear factor (NF)-κB. The fish protein and its enzymatic hydrolysates were not found to exert a cytotoxic effect on RAW264.7 macrophage cells; they inhibited the production of NO and cytokines in LPS-induced RAW264.7 cells. In particular, hydrolysates prepared by trypsin and α-chymotrypsin remarkably decreased the production of NO, cytokines, and PGE2. Reverse transcription-polymerase chain reaction analysis demonstrated that the decrease in NO and cytokine production was related to the inhibition of the mRNA expression of inducible nitric oxide synthase and cytokine (TNF-α, IL-6, and IL-1β) genes. Moreover, a reporter gene assay showed that the hydrolysates inhibited NF-κB nuclear translocation, and this inhibition was re-confirmed through inhibition of the mitogen-activated protein kinase pathway. The results suggested that the sweetfish-derived protein hydrolysates obtained using trypsin and α-chymotrypsin can be used as anti-inflammatory agents.

Effect of the combined treatment with gamma irradiation and sodium dichloroisocyanurate on postharvest Rhizopus soft rot of sweet potato

Rhizopus soft rot, caused by Rhizopus stolonifer, is a serious postharvest disease of sweet potatoes. Generally, the pathogen infects through wounds during storage and shipment after harvesting. To prevent losses, sweet potato packing houses have been using the fungicide dicloran, but many retail markets no longer allow dicloran residues. Recently, gamma-irradiation as a phytosanitary treatment was used to control plant pests and pathogens. In this study, we evaluated the combined effect of gamma irradiation and sodium dichloroisocyanurate (NaDCC) for control of Rhizopus soft rot. For an investigation of the effect of gamma irradiation and NaDCC treatment on conidia viability, we employed a dilution plate method. The results showed that gamma irradiation and NaDCC completely inhibited the growth of R. stolonifer at a 2.8 kGy dose and 20 ppm, respectively. The growth inhibition rate of R. stolonifer compared to the untreated control was 37.2% for the irradiation dose of 0.8 kGy, 61.5% for NaDCC at 10 ppm, and 73.6% for the combined treatment of 0.8 kGy irradiation dose and 10 ppm NaDCC. Based on the colour and weight loss measurement of the sweet potato slices, gamma irradiation treatment did not affect the physical quality. In an in vivo assay, the combination treatment of 0.6 kGy gamma irradiation and 10ppm NaDCC inhibited the fungal development. These results suggest that NaDCC treatment in combination with gamma irradiation is able to control Rhizopus soft rot disease of sweet potato or other fruits after harvesting.

Effects of Irradiation Temperature on the Sensory Quality Improvement of Gamma-irradiated Ganjang-gejang, Korean Traditional Marinated Raw Crab Portunus trituberculatus in Soybean Sauce

This study was conducted to confirm quality properties of sterilized Ganjang-gejang (marinated crab Portunus trituberculatus) with Korean soy sauce using by gamma irradiation and to improve quality of sterilized Ganjang-gejang. The Ganjang-gejang was irradiated at dose of 3, 6, 9, 12, and 15 kGy by gamma irradiation and there was evaluated in microbiological, physicochemical, and sensory properties. Total aerobic bacteria and fungi contents of non-irradiated samples were about 6 and 4 log CFU/g level, respectively. Gamma-irradiated samples at above 9 kGy did not contain aerobic bacteria or fungi at detection limit less than 2 log CFU/g, but sensory scores were significantly decreased depending on the irradiation dose. To improve the sensory qualities of gamma-irradiated Ganjang-gejang, the temperature was adjusted during sample irradiation. When samples were irradiated under freezing temperatures, especially on dry ice, the TBARS and the deterioration of sensory qualities of Ganjan-Gejang were reduced. Different odor patterns were observed among samples, as observed using electronic nose analysis system. The results of this study indicated that treatment with irradiation under low temperatures may help to preparing high-quality Ganjang-gejang.

Gamma irradiation of cultural artifacts for disinfection using Monte Carlo simulations

In this study, it has been investigated the disinfection of Korean cultural artifacts by gamma irradiation, simulating the absorbed dose distribution on the object with the Monte Carlo methodology. Fungal contamination was identified on two traditional Korean agricultural tools, Hongdukkae and Holtae, which had been stored in a museum. Nine primary species were identified from these items: Bjerkandera adusta, Dothideomycetes sp., Penicillium sp., Cladosporium tenuissimum, Aspergillus versicolor, Penicillium sp., Entrophospora sp., Aspergillus sydowii, and Corynascus sepedonium. However, these fungi were completely inactivated by gamma irradiation at an absorbed dose of 20kGy on the front side. Monte Carlo N Particle Transport Code was used to simulate the doses applied to these cultural artifacts, and the measured dose distributions were well predicted by the simulations. These results show that irradiation is effective for the disinfection of cultural artifacts and that dose distribution can be predicted with Monte Carlo simulations, allowing the optimization of the radiation treatment.

Erratum to: Accumulation of galloyl derivatives in a green alga, Spirogyra varians, in response to cold stress

One of the co-author’s middle initial, family name and affiliation contain an error. The correct name should be Frithjof C. Kupper not Frithjof D. Kupper while the affiliation should be Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll PA37 1QA, UK not Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Dunbeg PA371QA, UK. Corrected name and affiliation of the author are shown above and below.

Study of the Changes in Wood Properties by Gamma Irradiation

본 연구는 감마선 조사가 소나무(Pinus densiflrora), 느티나무(Zelkovas serrenata), 오동나무( Paulownia tomentosa)의 세포벽 열화, 셀룰로오스 결정화도, 휨 강도에 미치는 영향을 구명하기 위해 수행되었다. 각 목재시편들을 100 kGy 선량의 감마선 조사 후 주사전자현미경(scanning electron microscope; SEM) 관찰 결과, 목재 세포벽 열화는 관찰되지 않았으며 휨 강도 역시 현저한 변화가 나타나지 않았다. 감마선 조사에 의한 셀룰로오스 결정화도 역시 유의한 변화가 관찰되지 않았다. 이러한 감마선에 대한 목재의 높은 안전성은 감마선 조사 기술을 재질손상 없이 목재를 가해 중인 균류와 충류 구제를 위해 적용할 수 있음을 의미한다.