Describing size-related mortality and size distribution by nonparametric estimation and model selection using the Akaike Bayesian Information Criterion

When we calculate mortality along a gradient such as size, dividing into size classes and calculating rates for every class often involves a trade-off: fine class intervals produce fluctuating rates along the gradient, whereas broad ones may miss some trends within an interval. The same trade-off occurs when we want to illustrate size distribution by a histogram. This paper introduces nonparametric methods, published in a statistical journal, into forest ecology, in which the fine-class strategy is used in an extreme way: (1) a smoothly changing pattern is approximated by a fine step function, (2) the goodness-of-fit to the data and the smoothness along the gradient are formulated as a weighting sum within a Bayesian framework, (3) the Akaike Bayesian Information Criterion (ABIC) selects the weighting system that most appropriately balances the two demands, and (4) the values of the step function are optimized by the maximum likelihood method. The nonparametric estimates enable us to represent various patterns visually and, unlike parametric modeling, calculations do not demand the determination of a functional form. Mortality and size distribution analyses were conducted on 12-year forest tree monitoring data from a 4 ha permanent plot in an old-growth warm–temperate evergreen broad-leaved forest in Japan. From trees of 11 evergreen species with a diameter at breast height (DBH) greater than 5 cm, we found three types of trend with increasing DBH: decreasing, ladle-shaped and constant mortality. These patterns reflect variations in life history particular to each species.     

Formation of polar-body-like structures induced in polyspermic starfish oocytes that had been inseminated at the germinal vesicle stage

Immature starfish oocytes, which are arrested at the first meiotic prophase and contain a large nucleus called the germinal vesicle (GV), are known to accept multiple sperm on insemination. We found that if these polyspermic starfish oocytes are induced to mature, they often form small protrusion(s) adjacent to the first polar body emitted shortly earlier. We refer to these protrusion(s) as 'polar-body-like structures (PLS).' Fluorescent staining of PLS indicated that they were not merely cytoplasmic protrusions, but contained some chromatin. Maturing process of these polyspermic oocytes was examined by immnofluorescent staining, which showed that: (i) numerous sperm asters were observed after the onset of GV breakdown; (ii) before the first polar body (PB1) emission, a complex microtubular structure resembling a multipolar spindle was formed; and (iii) several isolated asters were observed after PB1 emission. These results indicate that PLS formation may be induced by interaction of meiosis-I spindle with paternal centrosomes incorporated at GV stage.     

Combination of hTERT and bmi-1, E6, or E7 induces prolongation of the life span of bone marrow stromal cells from an elderly donor without affecting their neurogenic potential

Murine bone marrow stromal cells differentiate not only into mesodermal derivatives, such as osteocytes, chondrocytes, adipocytes, skeletal myocytes, and cardiomyocytes, but also into neuroectodermal cells in vitro. Human bone marrow stromal cells are easy to isolate but difficult to study because of their limited life span. To overcome this problem, we attempted to prolong the life span of bone marrow stromal cells and investigated whether bone marrow stromal cells modified with bmi-1, hTERT, E6, and E7 retained their differentiated capability, or multipotency. In this study, we demonstrated that the life span of bone marrow stromal cells derived from a 91-year-old donor could be extended and that the stromal cells with an extended life span differentiated into neuronal cells in vitro. We examined the neuronally differentiated cells morphologically, physiologically, and biologically and compared the gene profiles of undifferentiated and differentiated cells. The neuronally differentiated cells exhibited characteristics similar to those of midbrain neuronal progenitors. Thus, the results of this study support the possible use of autologous-cell graft systems to treat central nervous system diseases in geriatric patients.     

Activation of extracellular signal-regulated kinase by ultraviolet is mediated through Src-dependent epidermal growth factor receptor phosphorylation. Its implication in an anti-apoptotic function.

Ultraviolet (UV) irradiation stimulates stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), which is a member of the mitogen-activated protein kinase (MAPK) superfamily and implicated in stress-induced apoptosis. UV also induces the activation of another MAPK member, extracellular signal-regulated kinase (ERK), which is typically involved in a growth-signaling cascade. However, the UV-induced signaling pathway leading to ERK activation, together with the physiological role, has remained unknown. Here we examined the molecular mechanism and physiological function of UV-induced ERK activation in human epidermoid carcinoma A431 cells that retain a high number of epidermal growth factor (EGF) receptors. UV-induced ERK activation was accompanied with the Tyr phosphorylation of EGF receptors, and both responses were completely abolished in the presence of a selective EGF receptor inhibitor (AG1478) or the Src inhibitor PP2 and by the expression of a kinase-dead Src mutant. On the other hand, SAPK/JNK activation by UV was partially inhibited by these inhibitors. UV stimulated Src activity in a manner similar to the ERK activation, but the Src activation was insensitive to AG1478. UV-induced cell apoptosis measured by DNA fragmentation and caspase 3 activation was enhanced by AG1478 and an ERK kinase inhibitor (U0126) but inhibited by EGF receptor stimulation by the agonist. These results indicate that UV-induced ERK activation, which provides a survival signal against stress-induced apoptosis, is mediated through Src-dependent Tyr phosphorylation of EGF receptors.     

Treatment of Mid‐Pregnant Mice with KRN633, an Inhibitor of Vascular Endothelial Growth Factor Receptor Tyrosine Kinase,Induces Abnormal Retinal Vascular Patterning in Their Newborn Pups

We previously reported that treatment of mid‐pregnant mice with KRN633, a vascular endothelial growth factor receptor tyrosine kinase inhibitor, caused fetal growth restriction resulting from diminished vascularization in the placenta and fetal organs. In this study, we examined how the treatment of mid‐pregnant mice with KRN633 affects the development and morphology of vascular components (endothelial cells, pericytes, and basement membrane) in the retinas of their newborn pups. Pregnant mice were treated with KRN633 (5 mg/kg) once daily from embryonic day 13.5 until the day of delivery. Vascular components were examined using immunohistochemistry with specific markers for each component. Radial vascular growth in the retina was slightly delayed until postnatal day 4 (P4) in the newborn pups of KRN633‐treated mothers. On P8, compared with the pups of control mothers, the pups of KRN633‐treated mothers exhibited decreased numbers of central arteries and veins and abnormal branching of the central arteries. No apparent differences in pericytes or basement membrane were observed between the pups of control and KRN633‐treated mothers. These results suggest that a critical period for determining retinal vascular patterning is present at the earliest stages of retinal vascular development, and that the impaired vascular endothelial growth factor signaling during this period induces abnormal architecture in the retinal vascular network     

A triangular loop of domain D1 of FlgE is essential for hook assembly but not for the mechanical function

The bacterial flagellar hook is a short, curved tubular structure made of FlgE. The hook connects the basal body as a rotary motor and the filament as a helical propeller and functions as a universal joint to smoothly transmit torque produced by the motor to the filament. Salmonella FlgE consists of D0, Dc, D1 and D2 domains. Axial interactions between a triangular loop of domain D1 (D1-loop) and domain D2 are postulated to be responsible for hook supercoiling. In contrast, Bacillus FlgE lacks the D1-loop and domain D2. Here, to clarify the roles of the D1-loop and domain D2 in the mechanical function, we carried out deletion analysis of Salmonella FlgE. A deletion of the D1-loop conferred a loss-of-function phenotype whereas that of domain D2 did not. The D1-loop deletion inhibited hook polymerization. Suppressor mutations of the D1-loop deletion was located within FlgD, which acts as the hook cap to promote hook assembly. This suggests a possible interaction between the D1-loop of FlgE and FlgD. Suppressor mutant cells produced straight hooks, but retained the ability to form a flagellar bundle behind a cell body, suggesting that the loop deletion does not affect the bending flexibility of the Salmonella hook.     

Biosynthesis of C-labeled branched polysaccharides by pestalotiopsis from C-labeled glucoses and the mechanism of formation

Biosynthesis of branched glucan by Pestalotiopsis from media containing D-(1-¹³C)glucose, D-(2-¹³C)glucose, D-(4-¹³C)glucose, D-(6-¹³C)glucose or a mixture of D-(1-¹³C)glucose and D-(2-¹³C)glucose was carried out to elucidate biosynthetic mechanism of branched polysaccharides. ¹³C NMR spectra of the labeled polysaccharides were determined and assigned. Analysis of ¹³C NMR spectra of glucitol acetates obtained from hydrolysates of the labeled branched polysaccharides indicated that transfer of labeling from C-1 to C-3 and C-6 carbons, from C-2 to C-1, C-3 and C-5 carbons, and from C-6 to C-1 carbon. From the results the percentages of routes via which the polysaccharide is biosynthesized are estimated. They show that the biosynthesis of the polysaccharide via the Embden-Meyerhof pathway and that from lipids and proteins are more active, and the pentose cycle is less active, than in the biosynthesis of cellulose and curdlan. As for the results, labeling at C-6 carbon in the branched polysaccharide cultured from D-(6-¹³C)glucose was low, compared to that of cellulose and curdlan.     

Phenylpiperidine-type γ-secretase modulators target the transmembrane domain 1 of presenilin 1

Amyloid-β peptide ending at the 42nd residue (Aβ42) is implicated in the pathogenesis of Alzheimer's disease (AD). Small compounds that exhibit selective lowering effects on Aβ42 production are termed γ-secretase modulators (GSMs) and are deemed as promising therapeutic agents against AD, although the molecular target as well as the mechanism of action remains controversial. Here, we show that a phenylpiperidine-type compound GSM-1 directly targets the transmembrane domain (TMD) 1 of presenilin 1 (PS1) by photoaffinity labelling experiments combined with limited digestion. Binding of GSM-1 affected the structure of the initial substrate binding and the catalytic sites of the γ-secretase, thereby decreasing production of Aβ42, possibly by enhancing its conversion to Aβ38. These data indicate an allosteric action of GSM-1 by directly binding to the TMD1 of PS1, pinpointing the target structure of the phenylpiperidine-type GSMs.     

Ergothioneine production with Aspergillus oryzae

To establish a reliable and practical ergothioneine (ERG) supply, we employed fermentative ERG production using Aspergillus oryzae, a fungus used for food production. We heterologously overexpressed the egt-1 and -2 genes of Neurospora crassa in A. oryzae and succeeded in producing ERG (231.0 mg/kg of media, which was 20 times higher than the wild type).

Abbreviations: ERG: ergothioneine; HER: hercynine; Cys-HER: hercynylcysteine-sulfoxide; SAM: S-adenosylmethionine; SAH: S-adenosylhomocysteine; l-His: l-histidine; l-Cys: l-cysteine; LC-ESI-MS: liquid chromatography-electrospray ionization-mass spectrometry