<Emphasis Type="Italic">Fusarium matuoi</Emphasis> sp. nov. and its teleomorph <Emphasis Type="Italic">Cosmospora matuoi</Emphasis> sp. nov.

A group of Fusarium isolates from slime flux similar to F. aquaeductuum produced unique, strongly curved, aseptate, C-shaped conidia. They were found to be identical to F. splendens nom. nud. Dried specimens from which F. splendens was originally isolated were reexamined and characterized as a new species of Cosmospora. Cosmospora matuoi sp. nov. is proposed for the teleomorph, and Fusarium matuoi sp. nov. is proposed for its anamorph.     

Ethanol production from xylose by recombinant Saccharomyces cerevisiae expressing protein engineered NADP+-dependent xylitol dehydrogenase

Effects of reversal coenzyme specificity toward NADP+ and thermostabilization of xylitol dehydrogenase (XDH) from Pichia stipitis on fermentation of xylose to ethanol were estimated using a recombinant Saccharomyces cerevisiae expressing together with a native xylose reductase from P. stipitis. The mutated XDHs performed the similar enzyme properties in S. cerevisiae cells, compared with those in vitro. The significant enhancement(s) was found in Y-ARSdR strain, in which NADP+-dependent XDH was expressed; 86% decrease of unfavorable xylitol excretion with 41% increased ethanol production, when compared with the reference strain expressing the wild-type XDH.     

Isolation of a LIM15/DMC1 homolog from the basidiomycete Coprinus cinereus and its expression in relation to meiotic chromosome pairing

The Escherichia coli gene recA is essential for homologous recombination and DNA repair, and homologs have been identified in eukaryotes. A basidiomycete, Coprinus cinereus, which has many advantages for the study of meiosis, was recently reported to have a homolog of one of these, RAD51. In the yeast Saccharomyces, mutations in the RAD5I gene cause defects in both somatic and meiotic cells. Based on this finding, we screened for a meiosis-specific homolog of recA, equivalent to Lilium LIM15 or Saccharomyces DMC1, in C. cinereus, and isolated a clone containing a 1.2-kb DNA fragment from a cDNA library constructed with Coprinus poly(A)⁺ RNA isolated from cells undergoing meiosis. The predicted amino acid sequence was 52% identical to the putative gene product of the lily cDNA clone LIM15 and 61% identical to Saccharomyces DMC1, and showed limited sequence similarity to the products of RAD52, 55, and 57. The synchrony of meiosis in Coprinus provides an ideal system for the investigation of differential gene expression in relation to meiosis and fruiting body development. Northern analysis indicated that Coprinus LIM15/DMC1 was expressed at meiotic prophase within 8 h after the onset of karyogamy, suggesting that the gene functions mostly at the stage at which the homologous chromosomes pair, but may not be essential at the point at which they recombine. The gene is not expressed in somatic cells. Received: 8 October 1998 / Accepted: 22 July 1999     

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.     

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.     

Patch establishment and development of a clonal plant,Polygonum cuspidatum,on Mount Fuji

Microsatellite analysis was used to investigate the patch establishment and development of Polygonum cuspidatum Sieb. et Zucc, a clonal herbaceous plant that dominates the primary succession on the southeast slope of Mount Fuji. Genotypes of P. cuspidatum in 155 patches at the study site differed from each other. This indicates that P. cuspidatum patches are initially established by seed dispersed on the bare scoria field, and not by clonal rhizome extension. Genetic differentiation was estimated using the FST values between subpopulations at the study site. There was almost no genetic differentiation between subpopulations, indicating the presence of massive gene flow. The pollen fathers of seeds and maternal genets of current-year seedlings were inferred from the microsatellite allele composition by a simple exclusion method. The wide, random distribution of pollen fathers suggests that pollen dispersal occurs over a broad area. Maternal analysis showed a tendency for seed dispersal to be biased to the area nearby and down slope from the mother plants. Patch establishment under massive gene flow may result from such pollen and seed dispersal. To understand the process of patch development, aerial photographs taken from 1962 to 1999 were compared, and then genets in each of 36 patches were identified from the microsatellite genotypes of P. cuspidatum shoots. The comparison of aerial photographs showed that most of the patches enlarged each year and that some neighbouring patches combined during growth. Genet analysis demonstrated a high correlation between patch area and the area of the largest genet within it, and that new genets were recruited at the patch periphery. These findings indicate that both vegetative and sexual reproduction, i.e. rhizome extension and the establishment of new seedlings, contribute to the development of P. cuspidatum patches.     

Nerve growth factor-induced glutamate release is via p75 receptor,ceramide, and Ca(2+) from ryanodine receptor in developing cerebellar neurons

Very little is known about the contribution of a low affinity neurotrophin receptor, p75, to neurotransmitter release. Here we show that nerve growth factor (NGF) induced a rapid release of glutamate and an increase of Ca2+ in cerebellar neurons through a p75-dependent pathway. The NGF-induced release occurred even in the presence of the Trk inhibitor K252a. The release caused by NGF but not brain-derived neurotrophic factor was enhanced in neurons overexpressing p75. Further, after transfection of p75-small interfering RNA, which down-regulated the endogenous p75 expression, the NGF-induced release was inhibited, suggesting that the NGF-induced glutamate release was through p75. We found that the NGF-increased Ca2+ was derived from the ryanodine-sensitive Ca2+ receptor and that the NGF-increased Ca2+ was essential for the NGF-induced glutamate release. Furthermore, scyphostatin, a sphingomyelinase inhibitor, blocked the NGF-dependent Ca2+ increase and glutamate release, suggesting that a ceramide produced by sphingomyelinase was required for the NGF-stimulated Ca2+ increase and glutamate release. This action of NGF only occurred in developing neurons whereas the brain-derived neurotrophic factor-mediated Ca2+ increase and glutamate release was observed at the mature neuronal stage. Thus, we demonstrate that NGF-mediated neurotransmitter release via the p75-dependent pathway has an important role in developing neurons.