Population dynamics of the harmful diatom Eucampia zodiacus Ehrenberg causing bleachings of Porphyra thalli in aquaculture in Harima-Nada, the Seto Inland Sea, Japan

The diatom Eucampia zodiacus Ehrenberg is one of the harmful diatom species which indirectly cause bleachings of Nori (Porphyra thalli) in aquaculture through competitive utilizing of nutrients (especially nitrogen) and resultant nutrient depletion in water columns during the bloom events. The seasonal changes in environmental factors, cell density and cell size of E. zodiacus were investigated for 4 years (April 2002–December 2005) to understand the population ecology of this diatom in Harima-Nada, the eastern part of the Seto Inland Sea, Japan. Vegetative cells of E. zodiacus were usually detected year-round. Total cell densities of E. zodiacus annually peaked from mid-February to early April, and high cell densities were observed in the whole water columns during the bloom-period. Nutrient concentrations decreased with the increase of cell density of E. zodiacus, and low nutrients concentrations continued throughout the E. zodiacus bloom-period. The average cell size (length of apical axis) of E. zodiacus populations ranged from 10.8 μm to 81.2 μm, and the restoration of cell size occurred once in autumn every year just after reaching the minimum cell size. In addition, its great seasonal regularity was confirmed by the decrease and restoration of its cell size through 4-year study period. Temperature and nutrients were suitable in autumn for the growth of E. zodiacus, its blooms never occur in that season. These results strongly suggest that E. zodiacus did not have a resting stage, and it spends autumn for size restoration and starts to bloom thereafter in Harima-Nada in winter and spring, causing fishery damage to Nori aquaculture by resulting nutrient deprivation.     

Four distinct trimeric forms of light-harvesting complex II isolated from the green alga Chlamydomonas reinhardtii

Photosynthesis Research - Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway present in a variety of genera including many epiphytic orchids. CAM is under circadian control...     

Essential role for ADAM19 in cardiovascular morphogenesis

Congenital heart disease is the most common form of human birth defects, yet much remains to be learned about its underlying causes. Here we report that mice lacking functional ADAM19 (mnemonic for a disintegrin and metalloprotease 19) exhibit severe defects in cardiac morphogenesis, including a ventricular septal defect (VSD), abnormal formation of the aortic and pulmonic valves, leading to valvular stenosis, and abnormalities of the cardiac vasculature. During mouse development, ADAM19 is highly expressed in the conotruncus and the endocardial cushion, structures that give rise to the affected heart valves and the membranous ventricular septum. ADAM19 is also highly expressed in osteoblast-like cells in the bone, yet it does not appear to be essential for bone growth and skeletal development. Most adam19(-/-) animals die perinatally, likely as a result of their cardiac defects. These findings raise the possibility that mutations in ADAM19 may contribute to human congenital heart valve and septal defects.     

Tie2/angiopoietin-1 signaling regulates hematopoietic stem cell quiescence in the bone marrow niche

The quiescent state is thought to be an indispensable property for the maintenance of hematopoietic stem cells (HSCs). Interaction of HSCs with their particular microenvironments, known as the stem cell niches, is critical for adult hematopoiesis in the bone marrow (BM). Here, we demonstrate that HSCs expressing the receptor tyrosine kinase Tie2 are quiescent and antiapoptotic, and comprise a side-population (SP) of HSCs, which adhere to osteoblasts (OBs) in the BM niche. The interaction of Tie2 with its ligand Angiopoietin-1 (Ang-1) induced cobblestone formation of HSCs in vitro and maintained in vivo long-term repopulating activity of HSCs. Furthermore, Ang-1 enhanced the ability of HSCs to become quiescent and induced adhesion to bone, resulting in protection of the HSC compartment from myelosuppressive stress. These data suggest that the Tie2/Ang-1 signaling pathway plays a critical role in the maintenance of HSCs in a quiescent state in the BM niche.     

Saturable, energy-dependent uptake of phenanthrene in aqueous phase by Mycobacterium sp. strain RJGII-135

The mechanism of uptake of phenanthrene by Mycobacterium sp. strain RJGII-135, a polycyclic hydrocarbon-degrading bacterium, was examined with cultures grown on phenanthrene (induced for phenanthrene metabolism) and acetate (uninduced). Washed cells were suspended in aqueous solutions of [9-(14)C]phenanthrene, and then the cells were collected by filtration. Low-level steady-state (14)C concentrations in uninduced cells were achieved within the first 15 s of incubation. This immediate uptake did not show saturation kinetics and was not susceptible to inhibitors of active transport, cyanide and carbonyl cyanide m-chlorophenylhydrazone. These results indicated that phenanthrene enters rapidly into the cells by passive diffusion. However, induced cells showed cumulative uptake over several minutes. The initial uptake rates followed saturation kinetics, with an apparent affinity constant (K(t)) of 26 +/- 3 nM (mean +/- standard deviation). Uptake of phenanthrene by induced cells was strongly inhibited by the inhibitors. Analysis of cell-associated (14)C-labeled compounds revealed that the concurrent metabolism during uptake was rapid and was not saturated at the substrate concentrations tested, suggesting that the saturable uptake observed reflects membrane transport rather than intracellular metabolism. These results were consistent with the presence of a saturable, energy-dependent mechanism for transport of phenanthrene in induced cells. Moreover, the kinetic data for the cumulative uptake suggested that phenanthrene is specifically bound by induced cells, based on its saturation with an apparent dissociation constant (K(d)) of 41 +/- 21 nM (mean +/- standard deviation). Given the low values of K(t) and K(d), Mycobacterium sp. strain RJGII-135 may use a high-affinity transport system(s) to take up phenanthrene from the aqueous phase.     

Size-dependent male–male competition for a spawning substrate between <Emphasis Type="Italic">Pseudorasbora parva</Emphasis> and <Emphasis Type="Italic">Pseudorasbora pumila</Emphasis>

Pseudorasbora parva, a species native to western Japan, has been accidentally introduced into eastern Japan, where P. pumila is indigenous. We investigated inter- and intraspecific, male–male competition between P. parva and P. pumila for acquisition of spawning substrates in an experimental setting. Within each species, males of larger standard length and heavier body weight were more successful in acquiring a substrate. Males of the two species competed, but the outcome was determined primarily by body weight. This interspecific, size-dependent, male–male competition might be an important factor in the species replacement of P. pumila by P. parva.     

Temperature sensitization of liposomes by use of N-isopropylacrylamide copolymers with varying transition endotherms

Three kinds of copolymers of N-isopropylacrylamide (NIPAM) with the same conformational transition temperature and varying transition endotherms were synthesized with N-acryloylpyrrolidine (APr), N,N-dimethylacrylamide (DMAM), and N-isopropylmethacrylamide (NIPMAM) as the comonomers. Two dodecyl groups were incorporated into the termini of these copolymers as an anchor for the fixation to a liposomal membrane. Egg yolk phosphatidylcholine liposomes having these copolymers were prepared and their temperature-sensitive contents release and association properties were investigated. While these copolymer exhibited a conformational transition at ca. 40 degrees C, DeltaH for the transition increased in the order of poly(APr-co-NIPAM) < poly(DMAM-co-NIPAM) < poly(NIPMAM-co-NIPAM). The liposomes containing poly(NIPMAM-co-NIPAM) showed a drastic release enhancement of entrapped calcein above the transition temperature, whereas the liposomes with poly(DMAM-co-NIPAM) and those with poly(APr-co-NIPAM) exhibited moderate and slight enhancement of calcein release above that temperature, respectively. On the contrary, the liposomes containing poly(APr-co-NIPAM) showed significant aggregation above the transition temperature, but the aggregation was hardly observed for the liposomes having poly(NIPMAM-co-NIPAM), indicating that poly(APr-co-NIPAM) more efficiently made the liposome surface hydrophobic. Thus, we concluded that the copolymer with a large DeltaH is suitable for obtaining functional liposomes with a temperature-sensitive contents release property, whereas the copolymer with a small DeltaH is appropriate for preparing functional liposomes with a temperature-sensitive surface property.     

Immunoglobulin treatment suppresses atherosclerosis in apolipoprotein E-deficient mice via the Fc portion

Atherosclerosis is associated with immune activation. Immunoglobulin is used for the treatment of immune-mediated diseases. The mechanisms and importance of the Fc portion of immunoglobulin upon experimental atherosclerosis in apolipoprotein E-deficient mice were examined. Experimental atherosclerosis was induced in mice fed a high-fat diet containing 0.3% cholesterol. Over 8, 12, and 16 wk, on alternate days, mice were treated with an intraperitoneal injection of either 1 g.kg-1.day-1 of human intact immunoglobulin or F(ab')2 fragments of human immunoglobulin. Fatty streak formation and fibrofatty plaques were markedly suppressed in mice that received intact immunoglobulin for 8, 12, and 16 wk. In contrast, atherosclerotic lesions were not ameliorated in mice that received F(ab')2 fragments. Immunohistochemical analysis revealed that macrophage accumulation in the fatty streak lesions was suppressed in mice received intact immunoglobulin but not in those that received F(ab')2 fragments. In addition, the cytotoxic activities of splenocytes from immunoglobulin-treated mice, but not from F(ab')2 fragment-treated mice, were significantly suppressed compared with those from human serum albumin-treated mice. Differences in lesion area did not correlate with any significant alterations in serum lipid levels. Immunoglobulin therapy markedly suppressed atherosclerosis due to Fc receptor-mediated anti-inflammatory and immunomodulating actions. The antiatherosclerotic effects of immunoglobulin may be related to the suppression of cytotoxic activity of atherogenic T cells and the reduction of macrophage accumulation in the lesions.     

A novel DNA polymerase inhibitor and a potent apoptosis inducer: 2-mono-O-acyl-3-O-(alpha-D-sulfoquinovosyl)-glyceride with stearic acid

Sulfo-glycolipids in the class of sulfoquinovosyl diacylglycerol (SQDG) including the stereoisomers are potent inhibitors of DNA polymerase alpha and beta. However, since the alpha-configuration of SQDG with two stearic acids (alpha-SQDG-C(18)) can hardly penetrate cells, it has no cytotoxic effect. We tried and succeeded in making a permeable form, sulfoquinovosyl monoacylglycerol with a stearic acid (alpha-SQMG-C(18)) from alpha-SQDG-C(18) by hydrolysis with a pancreatic lipase. alpha-SQMG-C(18) inhibited DNA polymerase activity and was found to be a potent inhibitor of the growth of NUGC-3 cancer cells. alpha-SQMG-C(18) arrested the cell cycle at the G1 phase, and subsequently induced severe apoptosis. The arrest was correlated with an increased expression of p53 and cyclin E, indicating that alpha-SQMG-C(18) induced cell death through a p53-dependent apoptotic pathway.