A rice dihydrosphingosine C4 hydroxylase (DSH1) gene, which is abundantly expressed in the stigmas, vascular cells and apical meristem, may be involved in fertility

Dihydrosphingosine C4 hydroxylase is a key enzyme in the biosynthesis of phytosphingosine, a major constituent of sphingolipids in plants and yeasts. The rice genome contains five homologue genes for dihydrosphingosine C4 hydroxylase, DSH1-DSH5, whose gene products show high degrees of homology to the yeast counterpart, SUR2. Among them, expression of DSH1, DSH2 and DSH4 was detected, and DSH1 and DSH4 complement the yeast sur2 mutation. The DSH1 gene was specifically and abundantly expressed in vascular bundles and apical meristems. In particular, very strong expression was detected in the stigmas of flowers. Repression of DSH1 expression by the antisense gene or RNA interference (RNAi) resulted in a severe reduction of fertility. In the transformants in which DSH1 expression was suppressed, significantly increased expression of DSH2 was found in leaves but not in pistils, suggesting that there was tissue-specific correlation between DSH1 and DSH2 expression. Our results indicate that the product of DSH1 may be involved in plant viability or reproductive processes, and that the phenotype of sterility is apparently caused by loss of function of DSH1 in the stigma. It is also suggested that there is a complex mechanism controlling the tissue-specific expression of the DSH1 gene.     

Granular tau oligomers as intermediates of tau filaments

Neurofibrillary tangles (NFTs) are pathological hallmarks of several neurodegenerative disorders, including Alzheimer's disease (AD). NFTs are composed of microtubule-binding protein tau, which assembles to form paired helical filaments (PHFs) and straight filaments. Here we show by atomic force microscopy that AD brain tissue and in vitro tau form granular and fibrillar tau aggregates. CD spectral analysis and immunostaining with conformation-dependent antibodies indicated that tau may undergo conformational changes during fibril formation. Enriched granules generated filaments, suggesting that granular tau aggregates may be an intermediate form of tau fibrils. The amount of granular tau aggregates was elevated in prefrontal cortex of Braak stage I cases compared to that of Braak stage 0 cases, suggesting that granular tau aggregation precedes PHF formation. Thus, granular tau aggregates may be a relevant marker for the early diagnosis of tauopathy. Reducing the level of these aggregates may be a promising therapy for tauopathies and for promoting healthy brain aging.     

Identification of MK-1925: A selective,orally active and brain-penetrable opioid receptor-like 1 (ORL1) antagonist

Structure–activity relationship studies directed toward improving the metabolic stability of compound 1 resulted in the identification of 3-[5-(3,5-difluorophenyl)-3-({[(1S,3R)-3-fluorocyclopentyl]amino}methyl)-4-methyl-1H-pyrazol-1-yl]propanenitrile 39 (MK-1925) as a selective, orally available and brain-penetrable opioid receptor-like 1 (ORL1) antagonist. The compound also showed in vivo efficacy after oral dosing. Therefore, compound 39 was selected to undergo further studies as a clinical candidate.     

Suppressive effect of a hot water extract of adzuki beans (Vigna angularis) on hyperglycemia after sucrose loading in mice and diabetic rats

A hot water extract obtained by boiling adzuki beans (Vigna angularis) to produce bean paste for Japanese cake showed inhibitory activity against alpha-glucosidase, alpha-amylase, maltase, sucrase, and isomaltase after HP-20 column chromatography. The IC(50) values for each hydrolylase were 0.78 mg/ml (alpha-amylase), 2.45 mg/ml (maltase), 5.37 mg/ml (sucrase), and 1.75 mg/ml (isomaltase). The active fraction showed potential hypoglycemic activity in both normal mice and streptozotocin (STZ)-induced diabetic rats after an oral administration of sucrose, but did not show any effect on the blood glucose concentration after glucose administration, suggesting that the active fraction suppressed the postprandial blood glucose level by inhibiting alpha-glucosidase and alpha-amylase, irrespective of the endogenous blood insulin level.     

Overexpression of CNP in chondrocytes rescues achondroplasia through a MAPK-dependent pathway

Achondroplasia is the most common genetic form of human dwarfism, for which there is presently no effective therapy. C-type natriuretic peptide (CNP) is a newly identified molecule that regulates endochondral bone growth through GC-B, a subtype of particulate guanylyl cyclase. Here we show that targeted overexpression of CNP in chondrocytes counteracts dwarfism in a mouse model of achondroplasia with activated fibroblast growth factor receptor 3 (FGFR-3) in the cartilage. CNP prevented the shortening of achondroplastic bones by correcting the decreased extracellular matrix synthesis in the growth plate through inhibition of the MAPK pathway of FGF signaling. CNP had no effect on the STAT-1 pathway of FGF signaling that mediates the decreased proliferation and the delayed differentiation of achondroplastic chondrocytes. These results demonstrate that activation of the CNP-GC-B system in endochondral bone formation constitutes a new therapeutic strategy for human achondroplasia.     

Citrulline enhances myofibrillar constituents expression of skeletal muscle and induces a switch in muscle energy metabolism in malnourished aged rats

Citrulline (Cit) actions on muscle metabolism remain unclear. Those latter were investigated using a proteomic approach on Tibialis muscles from male Sprague‐Dawley rats. At 23 months of age, rats were either fed ad libitum (AL group) or subjected to dietary restriction for 12 weeks. At the end of the restriction period, one group of rats was euthanized (R group) and two groups were refed for one week with a standard diet supplemented with nonessential amino acids group or Cit (CIT group). Results of the proteomic approach were validated using targeted Western blot analysis and assessment of gene expression of the related genes. Maximal activities of the key enzymes involved in mitochondrial functioning were also determined. Cit supplementation results in a significant increase in the protein expression of the main myofibrillar constituents and of a few enzymes involved in glycogenolysis and glycolysis (CIT vs. AL and R, p < 0.05). Conversely, the expression of oxidative enzymes from Krebs cycle and mitochondrial respiratory chain was significantly decreased (CIT vs. AL, p < 0.05). However, maximal activities of key enzymes of mitochondrial metabolism were not significantly affected, except for complex 1 which presented an increased activity (CIT vs. AL and R, p < 0.05). In conclusion, Cit supplementation increases expression of the main myofibrillar proteins and seems to induce a switch in muscle energy metabolism, from aerobia toward anaerobia.     

Phytosulfokine stimulates somatic embryogenesis in Cryptomeria japonica

Phytosulfokine (PSK), which has been identified as a plant growth factor, had a dramatic stimulatory effect on the formation of somatic embryos of sugi (Cryptomeria japonica) in the presence of polyethylene glycol. The resultant somatic embryos germinated with synchronous sprouting of cotyledons, hypocotyls and roots, and most of the seedlings grew normally. A cDNA clone for the precursor to the PSK peptide of C. japonica was identified in an expressed sequence tags database. Our results support the existence of a PSK signaling pathway in C. japonica.