Do-Hyung Kang

Chromene induces apoptosis via caspase-3 activation in human leukemia HL-60 cells

In this study, the potent anti-tumor effects of brown algae on human leukemia HL-60 cells were investigated. The Sargassum siliquastrum extract among the 14 species of brown algae exhibited profound growth inhibitory effect on HL-60 cells in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, therefore, S. siliquastrum was selected for use in further experiments. The highest inhibitory activity of S. siliquastrum on HL-60 cells was detected in the chloroform fraction, and the active compound was identified as a kind of chromene, sargachromanol E (SE). SE treatment showed significant growth inhibitory effects on HL-60 cells in a dose-dependent manner by inducing apoptosis, as evidenced by the formation of apoptotic bodies, fragmented DNA ladder, and the accumulation of DNA in the sub-G(1) phase of cell cycle. SE induced apoptosis was accompanied by downregulation of Bcl-xL, upregulation of Bax, activation of caspase-3, and cleavage of poly (ADP-ribose) polymerase (PARP). Moreover, z-DEVD-fmk, a caspase-3 inhibitor, significantly inhibited cell cytotoxicity, apoptotic characteristics such as apoptotic bodies, sub-G(1) DNA content, and cleavage of PARP induced by SE. These results suggest that SE exerts its growth inhibitory effects on HL-60 cells through caspase-3-mediated induction of apoptosis. Therefore, SE offers promising chemotherapeuric potential to prevent cancers such as human leukemia.

Quantitative assessment of reproductive condition of the Antarctic clam, Laternula elliptica (King & Broderip), using image analysis

Summary We quantitatively assessed the reproductive state of the Antarctic clam, L. elliptica, collected from a small cove on King George Island in the spawning season. Using computer-based image analysis, percentage gonad area (PGA), percentage egg area within a follicle (FI), and mean oocyte diameter (MOD) were determined from gonadal cross-sections prepared for histological studies. These indices were then compared on the basis of scores from 1 to 6 on a conventional maturity index (MI), which is scored using subjective criteria determined by microscopic examination. Clams collected during two different spawning periods were analyzed. The FI and MOD values differed significantly between the two groups, but MI and PGA values did not, suggesting that FI and MOD are the more reliable and sensitive indicators for differentiating reproductive condition. This study also showed that a planimetric technique using computer-based image analysis is fast, convenient to use, and better than the conventional MI at providing reliable quantitative information about L. elliptica reproduction. We also investigated whether these indices varied with body size. The FI and MOD values peaked in clams of 76 to 85 mm shell length, indicating that clams of this size have the highest reproductive output at spawning time. Therefore, animals of a standard size (76 to 85 mm) should be monitored seasonally or over a longer term.

Enhancement of Lipid Extraction from Marine Microalga, Scenedesmus Associated with High-Pressure Homogenization Process

Marine microalga, Scenedesmus sp., which is known to be suitable for biodiesel production because of its high lipid content, was subjected to the conventional Folch method of lipid extraction combined with high-pressure homogenization pretreatment process at 1200 psi and 35°C. Algal lipid yield was about 24.9% through this process, whereas only 19.8% lipid can be obtained by following a conventional lipid extraction procedure using the solvent, chloroformu2009:u2009methanol (2u2009:u20091, v/v). Present approach requires 30 min process time and a moderate working temperature of 35°C as compared to the conventional extraction method which usually requires >5 hrs and 65°C temperature. It was found that this combined extraction process followed second-order reaction kinetics, which means most of the cellular lipids were extracted during initial periods of extraction, mostly within 30 min. In contrast, during the conventional extraction process, the cellular lipids were slowly and continuously extracted for >5 hrs by following first-order kinetics. Confocal and scanning electron microscopy revealed altered texture of algal biomass pretreated with high-pressure homogenization. These results clearly demonstrate that the Folch method coupled with high-pressure homogenization pretreatment can easily destruct the rigid cell walls of microalgae and release the intact lipids, with minimized extraction time and temperature, both of which are essential for maintaining good quality of the lipids for biodiesel production.

The annual reproductive pattern of the Antarctic clam, Laternula elliptica from Marian Cove, King George Island

The annual reproductive cycle of the Antarctic soft-shelled clam, Laternula elliptica, in Marian Cove, King George Island was studied over a 2-year period from February 1998 to January 2000. Annual changes in the gametogenesis were investigated by measuring the percentage of area occupied by oocytes in a follicle [follicle index (FI)] and the oocyte size. In 1998, the monthly mean FI increased significantly from October to November, peaked in December, and decreased rapidly from December to January. In February and March 1999, degenerated eggs were observed in the spent follicles. Degeneration and resorption of residual eggs by phagocytosis occurred mostly in February and March in both 1998 and 1999, although the resorption process was observed year-round. The histology indicated that complete vitellogenic growth of L. ellpitica at Marian Cove takes at least a year and the clams spawn annually during the austral summer. The ripening and subsequent spawning of clams at Marian Cove in 1998 and 1999 coincided with the algal blooming (September–October 1998 and December and January 1999–2000) suggesting that in coastal Antarctica food supply is a crucial factor that governs gonad maturation and subsequent spawning along with the water temperature.

Immune response-related gene expression profile of a novel molluscan IκB protein member from Manila clam (Ruditapes philippinarum)

Mollusks lack an adaptive immune system and rely solely on the innate immune response. The nuclear factor-kappa B (NF-κB) signaling pathway is one of the most important components of the innate immune system and its activity is regulated by physical interaction with the inhibitor of NF-κB (IκB) protein. The manila clam, Ruditapes philippinarum (Rp), is a key species of the world’s aquaculture industry, and recent pathogenic threats, such as the Gram-negative lipopolysaccharide (LPS)-expressing Vibrio tapetis bacteria, have produced severe adverse economic impacts. Here, we describe identification, characterization and immune responses of novel IκB (Rp-IκB) in the manila clam. The Rp-IκB cDNA is comprised of a 1,032xa0bp open reading frame, which encodes 343 amino acid residues and has a predicted molecular mass of 38xa0kDa. The Rp-IκB protein exhibits typical structural features of IκB family members, including the IκB degradation motif, PEST sequence, and six ankyrin repeats. Phylogenetic analysis showed that manila clam and other known molluscan IκB proteins grouped together in the invertebrate cluster. Analysis of the tissue expression distribution revealed that Rp-IκB was ubiquitously expressed. However, immune challenge with V. tapetis and purified LPS endotoxin induced significant up-regulation of Rp-IκB expression in gill and hemocytes. These results indicated that Rp-IκB may play an important role in manila clam defense against bacterial infection.

Neuroprotective Effect of Phlorotannin Isolated from Ishige okamurae Against H2O2-Induced Oxidative Stress in Murine Hippocampal Neuronal Cells, HT22

The present study is designed to investigate the neuroprotective effect of a kind of phlorotannins, diphlorethohydroxycarmalol (DPHC) isolated from Ishige okamurae against hydrogen peroxide (H2O2)-induced oxidative stress in murine hippocampal neuronal cells, HT22. H2O2 treatment induced neurotoxicity, whereas DPHC prevented cells from H2O2-induced damage then restoring cell viability was significantly increased. DPHC slightly reduced the expression of Bax induced by H2O2 but recovered the expression of Bcl-xL as well as caspase-9 and -3 mediated PARP cleavage by H2O2. Intracellular reactive oxygen species (ROS) and lipid peroxidation was overproduced as the result of the addition of H2O2; however, these ROS generations and lipid peroxidation were effectively inhibited by addition of DPHC in a dose-dependent manner. Moreover, DPHC suppressed the elevation of H2O2-induced Ca2+ release. These findings indicate that DPHC has neuroprotective effects against H2O2-induced damage in neuronal cells, and that an inhibitory effect on ROS production may contribute to the underlying mechanisms.

Complete Genome Sequence of Bacteriophage phiAS7, a T7-Like Virus That Infects Aeromonas salmonicida subsp. salmonicida

ABSTRACT To date, a number of Myoviridae bacteriophages that infect Aeromonadaceae have been identified and characterized. However, the genome sequences of Aeromonas phages that not belong to the Myoviridae have not been investigated yet. Herein, we report the complete genome sequence of Aeromonas phage phiAS7, which belongs to the Podoviridae and infects Aeromonas salmonicida subsp. salmonicida.

Growth, Reproductive Condition, and Digestive Tubule Atrophy of Pacific Oyster Crassostrea gigas in Gamakman Bay off the Southern Coast of Korea

ABSTRACT Spat of Pacific oysters (Crassostrea gigas) were collected from Gamakman Bay, Korea, and raised in a spat hardening facility located in the low intertidal zone of the bay for a “hardening/stunting” period of 10 mo. Seasonal changes in growth, reproductive condition, and digestive tubule atrophy (DTA) of these “hardened/stunted” oysters were monitored for more than a year after transplanting to a suspended longline system in a grow-out area in the bay. After transplantation, the hardened/stunted oysters showed a logarithmic increase in shell size for the first 4 mo, from June to October, and growth remained stable from late fall to early spring. During the 12 mo of the grow-out, the shell size of the hardened/stunted oysters increased from 15.4–74.2 mm, and tissue weight increased from 0.49–12.85 g. Histological analysis revealed that gametogenesis of hardened/stunted oysters commenced as early as February when water temperature remained at 10°C, and spawning occurred from July to September when water temperature reached 25–27°C. DTA assessed from histological analysis was higher from September to February, when the chlorophyll a level in the bay was lower. These data suggest that seasonal fluctuations in water temperature and food availability in the water column are the 2 main environmental parameters governing reproduction and growth of oyster in Gamakman Bay, and DTA could be a useful biomarker for monitoring the nutritional condition of oysters.

Seasonal Changes in Reproduction and Biochemical Composition of the Cockle, Fulvia mutica Reeve (1884), in Cheonsu Bay off the West Coast of Korea

ABSTRACT n This is the first study of seasonal changes in gonad development and tissue biochemical composition of the cockle Fulvia mutica in Cheonsu Bay off the west coast of Korea. Gametogenesis commenced in December when the surface water temperature was 9.1°C. In May, the first discharge of oocytes was observed, and spawning continued until October. The condition index (CI), a ratio of tissue dry weight to shell dry weight, increased gradually from late May to July and declined dramatically in August and September, indicating that active discharge of gametes occurred in the bay during this period. Histology and the CI suggested that F. mutica spawning in Cheonsu Bay is continuous from early summer to early fall, with two spawning peaks in June and July, and September and October. All cockles examined in November were sexually inactive. The relatively low CI recorded in late fall to mid winter (November to January) coincided with high levels of ash and low levels of lipids and carbohydrates in the tissue, whereas protein levels remained unchanged. The observed spawning pattern of F. mutica in Cheonsu Bay suggests that the currently established timing for fishing closure, from July to September, should be expanded from June to October to protect earlyspawning broodstocks. This change may secure recruitment and lead to a subsequent increase of the wild cockle population in the bay.

Chromene suppresses the activation of inflammatory mediators in lipopolysaccharide-stimulated RAW 264.7 cells

Inflammation is complex process involving a variety of immune cells that defend the body from harmful stimuli. However, pro-inflammatory cytokines and inflammatory mediators can also exacerbate diseases such as cancer. The aim of this study was to identify a natural effective remedy for inflammation. We isolated a functional algal chromene compound from Sargassum siliquastrum, named sargachromanol D (SD). We evaluated the anti-inflammatory effect of SD on lipopolysaccharide (LPS)-exposed RAW 264.7 cells by measuring cell viability, cytotoxicity, and production of inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2), inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. SD inhibited production of NO and PGE2 from LPS-induced cells by preventing the expression of inflammatory mediators such as iNOS and COX-2 in a dose-dependent manner. Concurrently, levels of the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 were reduced with increasing concentrations of SD. In addition, SD inhibited the activation of NF-κB and mitogen-activated protein kinases (MAPKs) pathways in a concentration-dependent manner. These results indicate that SD inhibits LPS-stimulated inflammation by inhibition of the NF-κB and MAPKs pathways in macrophages.