Allelopathic effects of p-menthane-3,8-diols in Eucalyptus citriodora

The relationship between the allelopathic p-menthane-3,8-diols and the ontogenetic age in Eucalyptus citriodora was elucidated. The diols in the soil from a Eucalyptus grove were analysed by mass chromatography. Germination and growth inhibitory activities of the cis-diol against several higher plants were examined.     

Metabolism and biological functions of two phosphorylated sphingolipids, sphingosine 1-phosphate and ceramide 1-phosphate

Sphingolipids are major lipid constituents of the eukaryotic plasma membrane. Without certain sphingolipids, cells and/or embryos cannot survive, indicating that sphingolipids possess important physiological functions that are not substituted for by other lipids. One such role may be signaling. Recent studies have revealed that some sphingolipid metabolites, such as long-chain bases (LCBs; sphingosine (Sph) in mammals), long-chain base 1-phosphates (LCBPs; sphingosine 1-phosphate (S1P) in mammals), ceramide (Cer), and ceramide 1-phosphate (C1P), act as signaling molecules. The addition of phosphate groups to LCB/Sph and Cer generates LCBP/S1P and C1P, respectively. These phospholipids exhibit completely different functions than those of their precursors. In this review, we describe recent advances in understanding the functions of LCBP/S1P and C1P in mammals and in the yeast Saccharomyces cerevisiae. Since LCB/Sph, LCBP/S1P, Cer, and C1P are mutually convertible, regulation of not only the total amount of the each lipid but also of the overall balance in cellular levels is important. Therefore, we describe in detail their metabolic pathways, as well as the genes involved in each reaction.     

Amino acid substitutions in the s2 region enhance severe acute respiratory syndrome coronavirus infectivity in rat angiotensin-converting enzyme 2-expressing cells

To clarify the molecular basis of severe acute respiratory syndrome coronavirus (SARS-CoV) adaptation to different host species, we serially passaged SARS-CoV in rat angiotensin-converting enzyme 2 (ACE2)-expressing cells. After 15 passages, the virus (Rat-P15) came to replicate effectively in rat ACE2-expressing cells. Two amino acid substitutions in the S2 region were found on the Rat-P15 S gene. Analyses of the infectivity of the pseudotype-bearing S protein indicated that the two substitutions in the S2 region, especially the S950F substitution, were responsible for efficient infection. Therefore, virus adaptation to different host species can be induced by amino acid substitutions in the S2 region.     

p90 RSK-1 associates with and inhibits neuronal nitric oxide synthase

Evidence is presented that RSK1 (ribosomal S6 kinase 1), a downstream target of MAPK (mitogen-activated protein kinase), directly phosphorylates nNOS (neuronal nitric oxide synthase) on Ser847 in response to mitogens. The phosphorylation thus increases greatly following EGF (epidermal growth factor) treatment of rat pituitary tumour GH3 cells and is reduced by exposure to the MEK (MAPK/extracellular-signal-regulated kinase kinase) inhibitor PD98059. Furthermore, it is significantly enhanced by expression of wild-type RSK1 and antagonized by kinase-inactive RSK1 or specific reduction of endogenous RSK1. EGF treatment of HEK-293 (human embryonic kidney) cells, expressing RSK1 and nNOS, led to inhibition of NOS enzyme activity, associated with an increase in phosphorylation of nNOS at Ser847, as is also the case in an in vitro assay. In addition, these phenomena were significantly blocked by treatment with the RSK inhibitor Ro31-8220. Cells expressing mutant nNOS (S847A) proved resistant to phosphorylation and decrease of NOS activity. Within minutes of adding EGF to transfected cells, RSK1 associated with nNOS and subsequently dissociated following more prolonged agonist stimulation. EGF-induced formation of the nNOS-RSK1 complex was significantly decreased by PD98059 treatment. Treatment with EGF further revealed phosphorylation of nNOS on Ser847 in rat hippocampal neurons and cerebellar granule cells. This EGF-induced phosphorylation was partially blocked by PD98059 and Ro31-8220. Together, these data provide substantial evidence that RSK1 associates with and phosphorylates nNOS on Ser847 following mitogen stimulation and suggest a novel role for RSK1 in the regulation of nitric oxide function in brain.     

Chromosomal study of lettuce and its allied species (Lactuca spp., Asteraceae) by means of karyotype analysis and fluorescence in situ hybridization

In this study, in addition to the karyotype analysis, the chromosomal distributions of 5 S and 18 S rDNAs, and the Arabidopsis-type (T3AG3) telomeric sequences were detected by means of fluorescence in situ hybridization (FISH) to promote the information of chromosomal organization and evolution in the cultivated lettuce and its wild relatives, L. sativa, L. serriola, L. saligna and L. virosa. The karyotype analysis revealed the dissimilarity between L. virosa and the remaining species. In all four Lactuca species studied, one 5 S rDNA and two 18 S rDNA loci were detected. The simultaneous FISH of 5 S and 18 S rDNAs revealed that both rDNA loci of L. sativa, L. serriola and L. saligna were identical, however, that of L. virosa was different from the other species. These analyses indicate the closer relationships between L. sativa/L. serriola and L. saligna rather than L. virosa. Arabidopsis-type telomeric sequences were detected at both ends of their chromatids of all chromosomes not in the other regions. This observation suggests the lack of telomere-mediated chromosomal rearrangements among the Lactuca chromosomes.     

Discovery of (-)-6-[2-[4-(3-fluorophenyl)-4-hydroxy-1-piperidinyl]-1-hydroxyethyl]-3,4-dihydro-2(1H)-quinolinone--a potent NR2B-selective N-methyl D-aspartate (NMDA) antagonist for the treatment of pain

(-)-6-[2-[4-(3-Fluorophenyl)-4-hydroxy-1-piperidinyl]-1-hydroxyethyl]-3,4-dihydro-2(1H)-quinolinone was identified as an orally active NR2B-subunit selective N-methyl-d-aspartate (NMDA) receptor antagonist. It has very high selectivity for NR2B subunits containing NMDA receptors versus the HERG-channel inhibition (therapeutic index=4200 vs NR2B binding IC(50)). This compound has improved pharmacokinetic properties compared to the prototype CP-101,606.     

Roles of accumulated endogenous nitric oxide synthase inhibitors, enhanced arginase activity, and attenuated nitric oxide synthase activity in endothelial cells for pulmonary hypertension in rats

Nitric oxide (NO) has been suggested to play a key role in the pathogenesis of pulmonary hypertension (PH). To determine which mechanism exists to affect NO production, we examined the concentration of endogenous nitric oxide synthase (NOS) inhibitors and their catabolizing enzyme dimethylarginine dimethylaminohydrolase (DDAH) activity and protein expression (DDAH1 and DDAH2) in pulmonary artery endothelial cells (PAECs) of rats given monocrotaline (MCT). We also measured NOS and arginase activities and NOS protein expression. Twenty-four days after MCT administration, PH and right ventricle (RV) hypertrophy were established. Endothelium-dependent, but not endothelium-independent, relaxation and cGMP production were significantly impaired in pulmonary artery specimens of MCT group. The constitutive NOS activity and protein expression in PAECs were significantly reduced in MCT group, whereas the arginase, which shares l-arginine as a common substrate with NOS, activity was significantly enhanced in PAECs of MCT group. The contents of monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA), were increased in PAECs of MCT group. The DDAH activity and DDAH1, but not DDAH2, protein expression were significantly reduced in PAECs of MCT group. These results suggest that the impairment of cGMP production as a marker of NO production is possibly due to the blunted endothelial NOS activity resulting from the downregulation of endothelial NOS protein, accumulation of endogenous NOS inhibitors, and accelerated arginase activity in PAECs of PH rats. The decreased overall DDAH activity accompanied by the downregulation of DDAH1 would bring about the accumulation of endogenous NOS inhibitors.     

The beta-1,3-exoglucanase gene exgA (exg1) of Aspergillus oryzae is required to catabolize extracellular glucan, and is induced in growth on a solid surface

The biological role of ExgA (Exg1), a secretory beta-1,3-exoglucanase of Aspergillus oryzae, and the expression pattern of the exgA (exg1) gene were analyzed. The exgA disruptant and the exgA-overexpressing mutant were constructed, and phenotypes of both mutants were compared. Higher mycelial growth rate and conidiation efficiency were observed for the exgA-overexpressing mutant than for the exgA disruptant when beta-1,3-glucan was supplied as sole carbon source. On the other hand, no difference in phenotype was observed between them in the presence or absence of the inhibitors of cell wall beta-glucan remodeling when grown with glucose. exgA Expression was induced in growth on solid surfaces such as filter membrane and onion inner skin. A combination of poor nutrition and mycelial attachment to a hydrophobic solid surface appears to be an inducing factor for exgA expression. These data suggest that ExgA plays a role in beta-glucan utilization, but is not much involved in cell wall beta-glucan remodeling.